Circuit changeover switch

ABSTRACT

A circuit changeover switch  60 , which includes a drive device  10 , includes ceramic pumps  18   a  and  18   b , which alternately pressurize and depressurize operation fluid  100  within a fluid chamber  13   a  on opposite sides of an electrically conductive movable body  110 , to thereby move the movable body  110  within the flow chamber  13   a , whereby one of changeover electrodes  62   a  and  62   b  is electrically connected to a common electrode  61 . When the pressure of the operation fluid is increased and decreased at high speed by the ceramic pumps, micro channels  16   a  and  16   b  exhibit a high passage resistance, so that the pressure within the channel does not escape to an internal-pressure buffering chamber  15   a , and the movable body moves without fail. When the pressure of the operation fluid increases slowly due to expansion of the operation fluid, the micro channels exhibit a low passage resistance, so that an expanded portion of the operation fluid is led to the internal-pressure buffering chamber, and the pressure increase of the operation fluid is suppressed. A drive device which does not cause breakage of a pump chamber or a seal due to thermal expansion of operation fluid is provided.

TECHNICAL FIELD

[0001] The present invention relates to a circuit changeover switchwhich switches an electrical path by use of a drive device for moving amovable body through utilization of operation fluid.

BACKGROUND ART

[0002] In recent years, there have been developed micro motors, microsensors, micro switches, etc. which have sizes of several millimeters toseveral tens of microns and which are fabricated through utilization ofa technique for micro-machining of materials, such as a semiconductorfabrication technique, or by making use of piezoelectric material or alike material which can effect mutual conversion between electricalenergy and mechanical energy. These elementary devices can be widelyapplied to, for example, ink-jet printer heads, micro valves, flowsensors, pressure sensors, recording heads, actuators for trackingservos, on-chip biochemical analyzers, micro reactors, high-frequencycomponents, micro magnetic devices, micro relays, acceleration sensors,gyroscopes, drive devices, displays, and optical scanners (Nikkei MicroDevice, July 2000, pp 164-165).

[0003] In these micro machines, electrostatic force is often used asdrive force. Further, various types of drive sources have been studied,such as a type which utilizes distortion deformation of a piezoelectricmaterial caused through application of voltage thereto, a type whichutilizes changes in shape of a shape memory alloy, and a type whichutilizes changes in volume of liquid caused by phase change thereofinduced by heating. However, in micro mechanisms, force generated by adrive source and drive stroke become extremely small, and therefore, insome applications a mechanical amplification mechanism such as a levermust be combined with a drive source.

[0004] However, when the size of such a mechanical amplificationmechanism is reduced to that of a micro machine, wear or sticking, whichdoes not raise any problem in the case of a machine of ordinary size,raises a big problem. Further, since a micro machine having anamplification mechanism (drive function) such as a lever inevitablyrequires formation of a three-dimensional structure having a depth(height), micro machining of such a micro machine requires a longertime, and assembly of micro components requires a greater number ofsteps. For this reasons, some micro machines involve the problem of notbeing suitable for mass production.

[0005] Meanwhile, in order to be used as a circuit changeover switchthat functions as an electrical switch (or a relay), among theabove-described devices, there has been developed a mercury micro relayof a type which realizes switching operation through movement of amercury droplet and which utilizes, as a drive force for moving themercury droplet, pressure created upon instantaneous generation of abubble by means of heating by a micro heater (see, for example, J. Kimet al., Proc. 46th Annual Int. Relay Conf., Oak Brook, Ill., April 1998,pp. 19-1-19-8). This switch is reported to have various features, suchas a wide frequency range of DC to 10 GHz, high insulating resistanceand low insertion loss in the GHz band, and no signal bounce.

[0006] However, the above-described mercury micro relay of a bubblegeneration type has drawbacks, in that heat accumulates through heatingoperation and that a large amount of electrical power is consumed.

[0007] Accordingly, an object of the present invention is to provide acircuit changeover switch which is a device using operation fluid, whichmaintains the features of micro machines such as small size and lowpower consumption, which does not include a mechanical amplificationmechanism having intrinsic problems of wear and sticking, whichfacilitates mass production, and which hardly causes leakage ofoperation fluid under variation in atmospheric temperature. Anotherobject of the present invention is to provide a circuit changeoverswitch which is free from the problem of heat accumulation and whichenables high-speed changeover operation.

DISCLOSURE OF THE INVENTION

[0008] In order to achieve the above-described object, the presentinvention provides a circuit changeover switch comprising: a channelforming portion for forming a channel (i.e. a flow-passage formingportion for forming a flow passage), the channel accommodating anincompressible operation fluid and a movable body made of a substancedifferent from that of the operation fluid, and being substantiallydivided into two operation chambers by means of the movable body; a pairof pumps each including a pump chamber communicating with thecorresponding operation chamber and being filled with the operationfluid, an actuator provided for the pump chamber, and a diaphragmdeformed by the actuator, the operation fluid within the pump chamberbeing pressurized or depressurized through deformation of the diaphragm;an internal-pressure-buffering-chamber-forming portion for forming aninternal-pressure buffering chamber which accommodates the operationfluid and a compressible fluid for pressure buffering; and a microchannel portion for forming a micro channel which connects the channelof the channel forming portion and the internal-pressure bufferingchamber of the internal-pressure-buffering-chamber-forming portion, themicro channel exhibiting a high passage resistance against abruptpressure change of the operation fluid within the channel, to therebysubstantially prohibit passage of the operation fluid through the microchannel and exhibiting a low passage resistance against slow pressurechange of the operation fluid within the channel, to therebysubstantially permit passage of the operation fluid through the microchannel. The micro channel may connect the channel of thechannel-forming portion and the internal-pressure buffering chamber ofthe internal-pressure-buffering-chamber-forming portion directly, or viaanother portion (e.g., a connection passage for connecting the channeland the pump chamber, or a pump chamber). Further, three or more pumpsmay be provided.

[0009] By virtue of the above-described configuration, when thediaphragm is deformed by the actuator, the operation fluid within thechannel is pressurized or depressurized. At this time, when the pressureof the operation fluid changes abruptly, the micro channel exhibits ahigh passage resistance in order to substantially prohibit passage ofthe operation fluid through the micro channel. Therefore, the pressurechange of the operation fluid is transmitted to the movable body withinthe channel, so that the movable body moves. In contrast, when thepressure of the operation fluid changes slowly due to thermal expansionof the operation fluid caused by variation in the ambient temperature ordue to slow operation of the actuator, the micro channel exhibits a lowpassage resistance in order to substantially permit passage of theoperation fluid through the micro channel. Therefore, the operationfluid moves via the micro channel to the internal-pressure bufferingchamber, which accommodates a compressible fluid for pressure buffering.As a result, pressure increase of the operation fluid within the channelis suppressed, and it becomes possible to avoid breakage of the device(switch) due to excessive pressure of the operation fluid and to preventleakage of the operation fluid due to breakage of the device.

[0010] Preferably, the actuator includes a film-type piezoelectricelement comprising a piezoelectric/electrostrictive film or anantiferroelectric film and electrodes; and the diaphragm is formed ofceramic.

[0011] In this case, micro machining can be performed more easily, andcircuit changeover switches which are well suited for mass productionand which have excellent durability can be provided.

[0012] Preferably, the circuit changeover switch according to thepresent invention includes a first changeover electrode exposed to aportion of the channel of the channel forming portion; a secondchangeover electrode exposed to another portion of the channel of thechannel forming portion and electrically isolated from the firstchangeover electrode; and an electrode (common electrode) exposed to thechannel of the channel forming portion to face the first changeoverelectrode and the second changeover electrode via the channel (to beconnected with the first changeover electrode and the second changeoverelectrode through the movable body within the channel), wherein at leasta surface portion of the movable body is formed of an electricallyconductive material. In this case, the operation fluid must beelectrically non-conductive.

[0013] Preferably, the circuit changeover switch according to thepresent invention includes a first changeover electrode exposed to aportion of the channel of the channel forming portion; a secondchangeover electrode exposed to another portion of the channel of thechannel forming portion and electrically isolated from the firstchangeover electrode; an electrode exposed to the channel of the channelforming portion to face the first changeover electrode via the channel(to be connected with the first changeover electrode through the movablebody within the channel); and another electrode exposed to the channelof the channel forming portion to face the second changeover electrodevia the channel (to be connected with the second changeover electrodethrough the movable body within the channel), wherein at least a surfaceportion of the movable body is formed of an electrically conductivematerial.

[0014] Notably, in such a switch, no limitation is imposed on the numberof the changeover electrodes, so long as the number is not less thantwo.

[0015] By virtue of the above-described structure, the movable body ismoved between the first changeover electrode and the second changeoverelectrode by pumps each comprising a film-type piezoelectric element anda ceramic diaphragm, whereby an electric circuit (electric path) isswitched. Thus is provided a circuit changeover switch which exhibitsreduced electrical power consumption and which does not involve aproblem of heat accumulation, which would otherwise be caused by heatingby a micro heater. Further, since such a pump can be operated at highspeed and has excellent durability, a circuit changeover switch suitablefor portable information terminals, etc. can be provided.

[0016] In the above-described circuit changeover switch, preferably,each of the diaphragms of the pumps constitutes a portion of the wallsof the corresponding pump chamber and has a film surface in a commonplane; the channel of the channel forming portion forms a space whoselongitudinal axis lies in a plane parallel to the film surfaces of thediaphragms; the micro channel of the micro channel portion extends alonga direction parallel to the film surfaces of the diaphragms; and theinternal-pressure buffering chamber of theinternal-pressure-buffering-chamber-forming portion forms a space whoselongitudinal axis lies in a plane parallel to the film surfaces of thediaphragms and is connected with the channel of the channel formingportion via the micro channel of the micro channel portion.

[0017] When each of the pumps is configured in such a manner that adiaphragm formed of a single deformable plate member such as a ceramicsheet forms a portion of the walls of the pump chambers, the volume ofeach pump chamber is changed directly upon operation of thecorresponding actuator, whereby the operation fluid can be pressurizedor depressurized efficiently. Accordingly, it is preferable that each ofthe diaphragms of the pumps form a portion of the walls of thecorresponding pump chamber and have a film surface in the common plane.

[0018] Meanwhile, in order to produce a passage resistance having theabove-described characteristics, the micro channel must have a smallcross section. However, when the cross section of the micro channel isextremely small, high machining accuracy is required, thereby increasingthe production cost of the circuit changeover switch. By contrast, themicro channel can produce a passage resistance having theabove-described characteristics when the micro channel has an increasedlength. However, when the micro channel is extended only along adirection intersecting the film surface of the diaphragm (e.g., adirection perpendicularly intersecting the film surface of thediaphragm), the thickness of the circuit changeover switch increases.

[0019] In order to solve the above problem, the circuit changeoverswitch of the present invention employs the above-described structure inwhich the micro channel of the micro channel portion extends along adirection parallel to the film surface of the diaphragm; and the microchannel connects the channel of the channel forming portion and theinternal-pressure buffering chamber of theinternal-pressure-buffering-chamber-forming portion, each being a spacewhose longitudinal axis lies in a plane parallel to the film surface ofthe diaphragm. Since the above arrangement and configuration enableformation of the channel, the internal-pressure buffering chamber, andthe micro channel within a certain thickness, a circuit changeoverswitch (drive device) of small thickness (a thin type) can be provided.Further, since such a thin-type circuit changeover switch increases thesurface area of the circuit changeover switch relative to the overallvolume of the circuit changeover switch, heat generated upon operationcan be dissipated to the outside with ease, and the circuit changeoverswitch can operate stably.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is a sectional view of a drive device which serves as aportion of a circuit changeover switch according to a first embodimentof the present invention.

[0021]FIG. 2 is a plan view of the drive device shown in FIG. 1.

[0022]FIG. 3 is a sectional view of the drive device taken along line2-2 in FIG. 1.

[0023]FIG. 4 is a sectional view of the drive device shown in FIG. 1,showing an initial state thereof.

[0024]FIG. 5 is a sectional view of the drive device shown in FIG. 1,showing an operated state thereof.

[0025]FIG. 6 is a sectional view of the drive device shown in FIG. 1,showing another operated state thereof.

[0026]FIG. 7 is a sectional view of the drive device shown in FIG. 1,showing flow of operation fluid when the ambient temperature increases.

[0027]FIG. 8 is a sectional view of the drive device shown in FIG. 1,showing flow of the operation fluid when the ambient temperaturedecreases.

[0028]FIG. 9 is a view used for explaining an operation for finelyadjusting the position of a movable body of the drive device shown inFIG. 1.

[0029]FIG. 10 is a pair of time charts showing waveforms of voltageswhich are applied to piezoelectric films of the drive device shown inFIG. 1 for the purpose of fine adjustment of the position of the movablebody of the drive device.

[0030]FIG. 11 is a view used for explaining an operation for finelyadjusting the position of the movable body of the drive device shown inFIG. 1.

[0031]FIG. 12 is a view used for explaining an operation for finelyadjusting the position of the movable body of the drive device shown inFIG. 1.

[0032]FIG. 13 is a sectional view of a modification of the drive deviceshown in FIG. 1.

[0033]FIG. 14 is a sectional view showing a modification of a channel ofthe drive device shown in FIG. 1.

[0034]FIG. 15 is a sectional view of a drive device which serves as aportion of a circuit changeover switch according to a second embodimentof the present invention. FIG. 16 is a plan view of the drive deviceshown in FIG. 15.

[0035]FIG. 17 is a conceptional diagram showing a process of fabricatinga piezoelectric/electrostrictive actuator of the drive device shown inFIG. 15.

[0036]FIG. 18 is a conceptional diagram showing a different process offabricating a piezoelectric/electrostrictive actuator of the drivedevice shown in FIG. 15.

[0037]FIG. 19 is a conceptional diagram showing a process of fabricatingthe drive device shown in FIG. 15.

[0038]FIG. 20 is a conceptional diagram showing a process of fabricatingthe drive device shown in FIG. 15.

[0039]FIG. 21 is a sectional view of a drive device which serves as aportion of a circuit changeover switch according to a third embodimentof the present invention.

[0040]FIG. 22 is a sectional view of a drive device which serves as aportion of a circuit changeover switch according to a fourth embodimentof the present invention.

[0041]FIG. 23 is a sectional view of a drive device which serves as aportion of a circuit changeover switch according to a fifth embodimentof the present invention.

[0042]FIG. 24 is a plan view of the drive device shown in FIG. 23.

[0043]FIG. 25 is a sectional view of the drive device shown in FIG. 23,showing an operated state thereof.

[0044]FIG. 26 is a plan view of a modification of the drive device whichserves as a portion of the circuit changeover switch according to thefifth embodiment of the present invention.

[0045]FIG. 27 is a sectional view of one embodiment of the circuitchangeover switch of the present invention, showing an initial statethereof.

[0046]FIG. 28 is a sectional view of the circuit changeover switch shownin FIG. 27, showing a driven state thereof.

[0047]FIG. 29 is a system block diagram of a portable informationterminal to which the circuit changeover switch shown in FIG. 27 isapplied.

[0048]FIG. 30 is a sectional view of another embodiment of the circuitchangeover switch of the present invention, showing an initial statethereof.

[0049]FIG. 31 is a conceptional diagram showing a process of fabricatingthe circuit changeover switch shown in FIG. 30.

[0050]FIG. 32 is a conceptional diagram showing a different process offabricating the circuit changeover switch shown in FIG. 30.

[0051]FIG. 33 is a sectional view of still another embodiment of thecircuit changeover switch of the present invention, showing an initialstate thereof.

[0052]FIG. 34 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a sixth embodiment of thepresent invention.

[0053]FIG. 35 is a sectional view of the drive device taken along lineA5-A5 in FIG. 34.

[0054]FIG. 36 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a seventh embodiment of thepresent invention.

[0055]FIG. 37 is a sectional view of the drive device taken along lineA6-A6 in FIG. 36.

[0056]FIG. 38 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to an eighth embodiment of thepresent invention.

[0057]FIG. 39 is a sectional view of the drive device taken along lineA7-A7 in FIG. 38.

[0058]FIG. 40 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a ninth embodiment of thepresent invention.

[0059]FIG. 41 is a sectional view of the drive device taken along lineA8-A8 in FIG. 40.

[0060]FIG. 42 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a tenth embodiment of thepresent invention.

[0061]FIG. 43 is a sectional view of the drive device taken along lineA9-A9 in FIG. 42.

[0062]FIG. 44 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to an eleventh embodiment ofthe present invention.

[0063]FIG. 45 is a sectional view of the drive device taken along lineAA-AA in FIG. 44.

[0064]FIG. 46 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a twelfth embodiment of thepresent invention.

[0065]FIG. 47 is a sectional view of the drive device taken along lineAB-AB in FIG. 46.

[0066]FIG. 48 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a thirteenth embodiment ofthe present invention.

[0067]FIG. 49 is a sectional view of the drive device taken along lineAC-AC in FIG. 48.

[0068]FIG. 50 is a sectional view of the drive device taken along lineAD-AD in FIG. 48.

[0069]FIG. 51 is a plan view of a drive device which serves as a portionof a circuit changeover switch according to a fourteenth embodiment ofthe present invention.

[0070]FIG. 52 is a sectional view of the drive device taken along lineAE-AE in FIG. 51.

[0071]FIG. 53 is an enlarged sectional view of a modification of thepiezoelectric/electrostrictive film actuator applied to the drive deviceshown in FIG. 34, taken along line A5-A5 in FIG. 34.

[0072]FIG. 54 is an enlarged sectional view of the modification of thepiezoelectric/electrostrictive film actuator applied to the drive deviceshown in FIG. 34, taken along line AF-AF in FIG. 34.

BEST MODE FOR CARRYING OUT THE INVENTION

[0073] Embodiments of the circuit changeover switch containing the drivedevice according to the present invention will now be described withreference to the drawings. However, the present invention is not limitedto these embodiments, and on the basis of knowledge of persons withordinary skill in the art, various changes, modifications, andimprovements can be made without departing from the scope of the presentinvention. Notably, when the drive device is described, descriptions ofelectrodes are omitted.

[0074]FIG. 1 is a vertical sectional view of a drive device 10, whichserves as a portion of a circuit changeover switch according to a firstembodiment of the present invention; and FIG. 2 is a plan view of thedrive device 10. Notably, FIG. 1 is a sectional view of the drive device10 taken along line 1-1 in FIG. 2.

[0075] The drive device 10 comprises a ceramic base body 11 of asubstantially rectangular parallelepiped shape having sides whichrespectively extend along the X-axis, Y-axis, and Z-axis directions,which are mutually perpendicular; and a pair of piezoelectric films(piezoelectric/electrostrictive elements) 12 a and 12 b. The base body11 includes a channel forming portion 13, a pair of pump chambers 14 aand 14 b, an internal-pressure-buffering-chamber-forming portion 15, anda pair of micro channel portions 16 a and 16 b.

[0076] The channel forming portion 13 has a long axis along the X-axisdirection. As shown in FIG. 3, which is a sectional view of the basebody 11 taken along line 2-2 in FIG. 1 (along a plane parallel to theY-Z plane), the channel forming portion 13 forms a channel 13 a having asubstantially rectangular cross section. For example, the channel 13 ahas dimensions such that the width (along the Y-axis direction) W of thesubstantially rectangular cross section is 100 μm, the depth (along theZ-axis direction; i.e., height) H is 50 μm, and the longitudinal length(in the X-axis direction) L is 1 mm. Incompressible operation fluid(e.g., liquid such as water or oil) 100 and a movable body 110 areaccommodated within the channel 13 a. The movable body 110 is formedfrom a material ,such as magnetic material or liquid metal (e.g.,gallium alloy), differing from the operation fluid 100 and havingelectric conductivity at least at its surface portion. The channel 13 ais divided substantially into two operation chambers 13 a 1 and 13 a 2by means of the movable body 110. Within the channel 13 a, the movablebody 110 is present in the form of a single mass (liquid mass (vacuole),bubble, or micro solid) and, as shown in FIG. 3, forms very smallclearances S at the four corners of the rectangular cross section of thechannel 13 a in order to permit passage of the operation fluid 100therethrough.

[0077] The pump chamber 14 a is a space in the form of a cylinder whichhas a center axis extending along the Z-axis direction and is filledwith the operation fluid 100, the space being formed above the channel13 a in such a manner that a lower portion of the space communicateswith one end portion of the passage 13 a, located at the negative sidein the direction of the X-axis. For example, the pump chamber 14 a hasdimensions such that the bottom and top surfaces of the cylinder have aradius R of 0.5 mm, and the depth (height) h is 10 μm. A ceramicdiaphragm (diaphragm portion) 17 a having a thickness (height) d of 10μm is formed above the pump chamber 14 a.

[0078] The pump chamber 14 b has the same shape as the pump chamber 14 aand is formed above the channel 13 a in such a manner that a lowerportion of the space communicates with the other end portion of thepassage 13 a, located at the positive side in the direction of theX-axis. The pump chamber 14 b is filled with the operation fluid 100. Aceramic diaphragm 17 b having the same shape as that of the diaphragm 17a is formed above the pump chamber 14 b.

[0079] The piezoelectric film 12 a constitutes a ceramic pump 18 atogether with the pump chamber 14 a and the diaphragm 17 a. Thepiezoelectric film 12 a has a thickness D of 20 microns and assumes theshape of a circular thin plate which has a radius r slightly smallerthan the radius R of the pump chambers as viewed from above. Thepiezoelectric film 12 a is fixed to the upper surface of the diaphragm17 a in such a manner that the piezoelectric film 12 a is located abovethe pump chamber 14 a and that the center of the circular bottom surfaceof the piezoelectric film 12 a coincides with the center of the pumpchamber 14 a as viewed from above. When a voltage is applied tounillustrated paired electrodes formed to sandwich the piezoelectricfilm 12 a, the piezoelectric film 12 a increases and decreases thevolume of the pump chamber 14 a by deforming the diaphragm 17 a, tothereby pressurize or depressurize the operation fluid 100 within thepump chamber 14 a. Notably, the piezoelectric film 12 a is polarized inthe positive direction of the Z-axis.

[0080] The piezoelectric film 12 b has the same shape as thepiezoelectric film 12 a. The piezoelectric film 12 b constitutes aceramic pump 18 b together with the pump chamber 14 b and the diaphragm17 b. That is, the piezoelectric film 12 b is fixed to the upper surfaceof the diaphragm 17 b in such a manner that the piezoelectric film 12 bis located above the pump chamber 14 b. When a voltage is applied tounillustrated paired electrodes, the piezoelectric film 12 b increasesand decreases the volume of the pump chamber 14 b by deforming thediaphragm 17 b, to thereby pressurize or depressurize the operationfluid 100 within the pump chamber 14 b. Notably, the piezoelectric film12 b is also polarized in the positive direction of the Z-axis.

[0081] The internal-pressure-buffering-chamber-forming portion 15 formsan internal-pressure buffering chamber 15 a which assumes asubstantially elliptical shape having a major axis along the X-axisdirection as viewed from above. The internal-pressure buffering chamber15 a has a length along the X-axis greater than the length L of thechannel 13 a and a length along the Y-axis (minor axis) directiongreater than the width W of the channel 13 a, and has a substantiallyrectangular cross section, as shown in FIG. 3. The internal-pressurebuffering chamber 15 a is formed within the base body 11 to be locatedbelow the channel 13 a (on the Z-axis negative direction side of thechannel 13 a) in such a manner that the major axis of the chamber 15 acoincides with the center axis of the channel 13 a as viewed from above.The above-described operation fluid 100 fills a substantially centralportion of the chamber 15 a with respect to the X-axis direction. Acompressible fluid for pressure buffering (hereinafter may be referredto as a “compressible fluid”) 120 (having a compressibility considerablylower than that of the operation fluid 100) fills the peripheralportions of the chamber 15 a. In the present embodiment, thecompressible fluid 120 is vapor of the operation fluid 100. However, apredetermined amount of an inert gas may be mixed into the vapor, or thevapor may be replaced with a gas not containing the vapor.

[0082] The micro channel portion 16 a forms a micro channel 16 a 1 whichextends along the Z-axis direction and assumes the shape of a hollowcylinder. The micro channel 16 a 1 connects the left-hand operationchamber 13 a 1 of the channel 13 a with the internal-pressure bufferingchamber 15 a. The micro channel 16 a 1 is also filled with the operationfluid 100. For example, the micro channel 16 a 1 has dimensions suchthat the cylinder has a radius of 15 μm, and the length along the Z-axisdirection (height of the cylinder) is 100 μm. The shape of the microchannel 16 a 1 is selected to produce a fluid resistance greater thanthat produced by the channel 13 a. Specifically, the micro channel 16 a1 has a so-called throttle function which produces a high passageresistance against abrupt pressure change of the operation fluid 100within the channel 13 a, to thereby substantially prohibit passage(movement) of the operation fluid 100 toward the internal-pressurebuffering chamber 15 a, and which produces only a small passageresistance against slow pressure change of the operation fluid 100within the channel 13 a, to thereby substantially permit passage(movement) of the operation fluid 100 toward the internal-pressurebuffering chamber 15 a.

[0083] The micro channel portion 16 b forms a micro channel 16 b 1,which has the same shape as the micro channel 16 a 1. The micro channel16 b 1 connects the right-hand operation chamber 13 a 2 of the channel13 a with the internal-pressure buffering chamber 15 a. The microchannel 16 b 1 is also filled with the operation fluid 100. The microchannel 16 b 1 also has a throttle function identical to that of themicro channel 16 a 1.

[0084] As described above, the operation fluid 100 continuously fillsthe channel 13 a, the pair of pump chambers 14 a and 14 b, the pair ofmicro channels 16 a 1 and 16 b 1, and a portion of the internal-pressurebuffering chamber 15 a, which communicates with the channel 13 a via thepair of micro channels 16 a 1 and 16 b 1. Further, the vapor 120 of theoperation fluid 100 fills the spaces of the internal-pressure bufferingchamber 15 a that are not filled with the operation fluid 100.

[0085] Next, operation of the drive device 10 configured as describedabove will be described with reference to FIGS. 4 to 7, which showdifferent operation states. FIG. 4 shows an initial state of the drivedevice 10 in which drive voltage is applied to none of the electrodes ofthe piezoelectric films 12 a and 12 b. In this case, since both the pumpchambers 14 a and 14 b maintain their initial volumes, the operationfluid 100 charged into the pump chambers 14 a and 14 b and the channel13 a is neither pressurized or depressurized. Consequently, the movablebody 110 accommodated within the channel 13 a remains at the initialposition (at the substantially central portion of the channel 13 a withrespect to the X-axis direction).

[0086] During drive, as shown in FIG. 5, a voltage is applied to theupper and lower electrodes of the piezoelectric film 12 a disposed onthe diaphragm 17 a of the pump chamber 14 a in such a manner that theupper electrode assumes a positive polarity and the lower electrodeassumes a negative polarity. Simultaneously, a voltage is applied to theupper and lower electrodes of the piezoelectric film 12 b disposed onthe diaphragm 17 b of the pump chamber 14 b in such a manner that theupper electrode assumes a negative polarity and the lower electrodeassumes a positive polarity.

[0087] As a result, the piezoelectric film 12 a contracts along thetransverse direction (i.e., in a plane substantially parallel to the X-Yplane, or in the direction perpendicular to the direction of thethickness D of the piezoelectric film 12 a), so that the diaphragm 17 aabove the pump chamber 14 a bends and deforms downward to thereby reducethe volume of the pump chamber 14 a. As a result, the operation fluid100 within the pump chamber 14 a is pressurized, so that the operationfluid 100 flows from the pump chamber 14 a to the operation chamber 13 a1 of the channel 13 a. Simultaneously, the piezoelectric film 12 bexpands along the transverse direction (i.e., in a plane substantiallyparallel to the X-Y plane), so that the diaphragm 17 b bends and deformsupward to thereby increase the volume of the pump chamber 14 b. As aresult, the operation fluid 100 within the pump chamber 14 b isdepressurized, so that the operation fluid 100 flows from the operationchamber 13 a 2 of the channel 13 a to the pump chamber 14 b.Accordingly, due to the pressure difference between the pump chambers 14a and 14 b, the movable body 110 accommodated within the channel 13 amoves from the operation chamber 13 a 1 (pump chamber 14 a) toward theoperation chamber 13 a 2 (pump chamber 14 b) (i.e., in the positivedirection of the X-axis).

[0088] Further, when, as shown in FIG. 6, a voltage is applied to theupper and lower electrodes of the piezoelectric film 12 a in such amanner that the upper electrode assumes a negative polarity and thelower electrode assumes a positive polarity, and simultaneously, avoltage is applied to the upper and lower electrodes of thepiezoelectric film 12 b in such a manner that the upper electrodeassumes a positive polarity and the lower electrode assumes a negativepolarity, the operation fluid 100 within the pump chamber 14 b ispressurized, and the operation fluid 100 within the pump chamber 14 a isdepressurized. Due to the pressure difference, the movable body 110moves from the operation chamber 13 a 2 (pump chamber 14 b) toward theoperation chamber 13 a 1 (pump chamber 14 a) (i.e., in the negativedirection of the X-axis).

[0089] During such ordinary driving, pressurization and depressurizationof the pump chambers 14 a and 14 b are performed at high speed byvarying the voltages applied to the piezoelectric films 12 a and 12 b athigh speed (i.e., by having larger speed at which the applied voltagesare increased and decreased). As a result, the passage resistances ofthe micro channels 16 a 1 and 16 b 1 become sufficiently large, and theoperation fluid 100 within the channel 13 a does not move to (gothrough), or return from, the micro channels 16 a 1 and 16 b 1.Therefore, the pressure difference generated between the operationchambers 13 a 1 and 13 a 2 of the channel 13 a acts on the movable body110 without decreasing (without generation of so-called pressureescaping). Accordingly, the movable body 110 moves without fail.

[0090] Incidentally, in the case of a drive device which does notinclude the micro channels 16 a 1 and 16 b 1 and the internal-pressurebuffering chamber 15 a, when the operation fluid 100 thermally expandsdue to an increase in the environment temperature of the drive device,the pressure of the operation fluid 100 becomes excessive, possiblyraising a problem such that the pump chambers 14 a and 14 b increase involume, and the diaphragms 17 a and 17 b are pushed up and broken.Further, in the case in which the base body 11 is formed of an assemblyof bonded ceramic sheets, there may arise the problem such that a bondedportion (the seal of the bonded portion) is broken, and the operationfluid 100 leaks.

[0091] By contrast, the drive device 10 according to the presentinvention is provided with the micro channels 16 a 1 and 16 b 1 and theinternal-pressure buffering chamber 15 a. In addition, since thetemperature increase of the operation fluid 100 occurs slowly, thepressure of the operation fluid 100 increases slowly. Accordingly, asindicated by arrows in FIG. 7, an amount of the operation fluid 100corresponding to expansion due to temperature elevation flows into theinternal-pressure buffering chamber 15 a via the micro channels 16 a 1and 16 b 1, which produce an extremely low passage resistance againstsuch slow increase in pressure of the operation fluid 100. Within theinternal-pressure buffering chamber 15 a, the vapor 120 of the operationfluid 100 is compressed, and pressure increase occurs. However, thepressure increase of the operation fluid 100 is slight, because thecompressibility of gas is lower than that of liquid. Accordingly, therecan be avoided the situation in which the diaphragms 17 a and 17 b abovethe pump chambers 14 a and 14 b are pushed up and broken and thesituation in which a seal of the bond-assembled portion is broken, withresultant leakage of the operation fluid 100. Further, when theoperation fluid 100 thermally contracts due to a decrease in theenvironmental temperature of the drive device 10, as indicated by arrowsin FIG. 8, the operation fluid 100 returns from the internal-pressurebuffering chamber 15 a to the channel 13 a via the micro channels 16 a 1and 16 b 1, because the temperature decrease of the operation fluid 100occurs slowly.

[0092] As described above, by virtue of provision of the micro channels16 a 1 and 16 b 1 and the internal-pressure buffering chamber 15 a, thedrive device 10 can be used within a wide temperature range, and canhave enhanced reliability and durability.

[0093] Next, an operation which the drive device 10 performs in theinitial state in order to finely adjust the position of the movable body110 will be described by reference to FIGS. 9 to 12. Here, it is assumedthat, as shown in FIG. 9, in the initial state the movable body 110remains at a position deviated to the side toward the piezoelectric film12 a. Such a state may result from variation, or erroneous work,involved in a fabrication process which will be described later;specifically, in a step of placing the movable body 110 in the channel13 a.

[0094] First, during a period of time from t1 to t2 shown in FIG. 10,voltages Va and Vb, which change at high speed, are applied to (theelectrodes of) the piezoelectric films 12 a and 12 b, respectively. Forexample, the applied voltage Va is a drive voltage whose absolute valueincreases from 0 V to 50 V during a period of 1 to 20 μsec and which hasa polarity such that the upper electrode becomes the positive side andthe lower electrode becomes the negative side. Similarly, the appliedvoltage Vb is a drive voltage whose absolute value increases from 0 V to50 V during a period of 1 to 20 μsec and which has a polarity such thatthe upper electrode becomes the negative side and the lower electrodebecomes positive side. As a result, as shown in FIG. 11, the operationfluid 100 is pressurized in the pump chamber 14 a and is depressurizedin the pump chamber 14 b, so that the movable body 110 moves toward thecenter (toward the pump chamber 14 b). In this case, since the appliedvoltages Va and Vb change at high speed, the passage resistances of themicro channels 16 a 1 and 16 b 1 become sufficiently large, and thus theoperation fluid 100 within the channel 13 a does not move to, or returnfrom, the micro channels 16 a 1 and 16 b 1.

[0095] Subsequently, during a short period of time from t2 to t3 shownin FIG. 10, the applied voltages Va and Vb are maintained constant; andduring a subsequent period of time from t3 to t4, the absolutes valuesof the applied voltages Va and Vb are decreased slowly to 0 V over aperiod of, for example, about 0.1 to 1 sec. In this case, since thepassage resistances of the micro channels 16 a 1 and 16 b 1 becomesmall, as shown in FIG. 12, the operation fluid 100 within theright-hand operation chamber 13 a 2 of the channel 13 a flows into theinternal-pressure buffering chamber 15 a via the micro channel 16 b 1,and the operation fluid 100 within the internal-pressure bufferingchamber 15 a flows into the left-hand operation chamber 13 a 1 of thechannel 13 a via the micro channel 16 a 1. That is, the pressure changeof the operation fluid 100 becomes sufficiently slow such that pressureescapes via the micro channels 16 a 1 and 16 b 1, and the internalpressure of the pump chamber 14 a and 14 b and the channel 13 a hardlychanges. Thus, the movable body 110 can be maintained stationary.Alternatively, as compared with the moving distance L0 of the movablebody 110 upon application of voltages during the period of t1 to t2, thereturn distance L1 of the movable body 110 during the period of t3 to t4can be reduced to about one-tenth (L1=L0/10).

[0096] Through performing the above-described operation once or aplurality of times, the movable body 110 can be positioned at a desiredinitial position. Further, the movable body 110 can be moved to stop ata desired position through appropriate selection of the peak values Vpand −Vp of the applied voltages Va and Vb shown in FIG. 10, the voltagechange speed at which the applied voltages Va and Vb are changed to thepeak values Vp and −Vp, and the voltage change speed at which theapplied voltages Va and Vb are changed from the peak values Vp and −Vpto 0 V.

[0097] In the above-described embodiment, through application ofvoltages to the piezoelectric films 12 a and 12 b, electric fields areapplied to the piezoelectric films 12 a and 12 b in the positivedirection (in the present embodiment, Z-axis positive direction) and thenegative direction (Z-axis negative direction), respectively. However,in some cases, application of such electric fields is not desirable,because an electric field of a direction opposite the polarizationdirection of the piezoelectric films 12 a and 12 b cancels thepolarization if the intensity of the electric field exceeds that of acoercive field. In view of this, a bias voltage may be applied so as toestablish the initial state of the drive device 10. In this case, thedrive device 10 can be driven through use of electric fields of the samedirection as that of the polarization. Specifically, for example, thepotential of the lower electrode is maintained at 0 V, which is areference potential, and a bias voltage of 25 V is applied to the upperelectrode to establish an initial state. When the potential of the upperelectrode of either one of piezoelectric film 12 a or 12 b is increasedto 50 V, an electric field is applied to that piezoelectric film in thesame direction as the polarization direction, so that the piezoelectricfilm contracts. As a result, the diaphragm 17 a or 17 b located underthe piezoelectric film bends and deforms downward, and the correspondingpump chamber 14 a or 14 b pressurizes the operation fluid 100.Simultaneously, when the potential of the upper electrode of the otherof the piezoelectric films 12 a and 12 b is decreased to 0 V, thecontraction of that piezoelectric film is cancelled. Accordingly, thediaphragm 17 a or 17 b located under the piezoelectric film bends anddeforms upward with respect to the initial state, and the correspondingpump chamber 14 a or 14 b depressurizes the operation fluid 100.

[0098] Next, a modification of the drive device according to the firstembodiment will be described with reference to FIG. 13. The drive device10-1 according to this modification differs from the drive device 10shown in FIG. 1 only in that a base body 11-1 of the drive device 10-1includes a single micro channel 16 a 1, whereas the base body 11 of thedrive device 10 has the pair of micro channels 16 a 1 and 16 b 1. Thisconfiguration can be employed only in the case in which the gap(clearance S shown in FIG. 3) between the movable body 110 and thechannel 13 a can have a cross section equal to or greater than apredetermined value. Since this configuration can halve labor and timerequired to machine the micro channels, the drive device 10-1 can befabricated at lower cost. However, in this modification, the stationaryposition of the movable body 110 in the initial state in which novoltage is applied to the drive device 10-1 is difficult to control. Inrelation to this point, the drive device 10 of the first embodiment isconsidered superior.

[0099] Note that in addition to the above-described gap (clearance S), amicro groove M may be formed in the wall surface of the channel 13 a, asshown in, for example, FIG. 14, which shows a cross section of thechannel 13 a. The micro groove M may be configured in such a manner thatthe operation fluid 100 can enter the groove M insofar as the pressurechange of the operation fluid 100 is slow and the surface of the movablebody 110 cannot enter the micro groove M. Notably, the micro groove Mcan be applied to other embodiments of the present invention, and thenumber and shape of the micro grooves may be selected appropriately.

[0100] Further, the piezoelectric/electrostrictive film type actuatorfor a display device disclosed in, for example, Japanese PatentApplication Laid-Open (kokai) No. 10-78549 can be applied to thepiezoelectric films 12 a and 12 b, the diaphragms 17 a and 17 b, and thepump chambers 14 a and 14 b of the above-described drive devices 10 and10-1 (and drive devices of other embodiments which will be describedlater). Since this actuator is small and can produce a largepressurizing force, it is suitable for the drive device of the presentinvention. Further, when the drive operation which has been describedwith reference to FIGS. 4 to 6 is performed, an important considerationis that the piezoelectric films 12 a and 12 b be formed of apiezoelectric material which has a large coercive electric field,because of occurrence of a state in which voltage is applied to thepiezoelectric films 12 a and 12 b in the direction opposite thepolarization direction of the piezoelectric films 12 a and 12 b. Whenthe intensity of a coercive electric field is low, the polarization maybe disturbed through application of voltage in the direction oppositethe polarization direction.

[0101] In order to reduce the amount of thermal expansion andcontraction of the operation fluid 100 stemming from variation in theenvironmental temperature, it is desirable that the volumes of the pumpchambers 14 a and 14 b be close to a minimum required value. In order toachieve this, the method disclosed in Japanese Patent ApplicationLaid-Open (kokai) No. 9-229013 is preferably used to fabricate adiaphragm substrate used in the process of fabricating theabove-described piezoelectric/electrostrictive film type actuator,because the disclosed method can reduce the depths of the pump chambers14 a and 14 b to about 5 (minimum) to 10 μm.

[0102] Next, a drive device 20, which serves as a portion of a circuitchangeover switch according to a second embodiment of the presentinvention, will be specifically described, together with a method offabricating the device. FIG. 15 is a vertical sectional view of thedrive device 20, and FIG. 16 is a plan view of the drive device 20.Notably, FIG. 15 is a sectional view of the drive device 20 taken alongline 3-3 in FIG. 16. In the following description, the same structuralportions in respective embodiments are denoted by the same referencenumerals, and their detailed descriptions are not repeated.

[0103] The drive device 20 includes a base body 21 having a channel 13 awhich is formed to be exposed at the upper surface thereof; a connectionplate (connection substrate) 22 disposed on the base body 21 and formedof a ceramic thin plate; and a pair of ceramic pumps 23 a and 23 bdisposed on the connection plate 22.

[0104] The connection plate 22 includes left-hand and right-hand channelconnection holes 22 a and 22 b, which are formed at positions separatedfrom each other along the X-axis direction and each assume the shape ofa hollow cylinder. The bottom ends of the channel connection holes 22 aand 22 b are connected to the opposite end portions of the channel 13 awith respect to the X-axis direction.

[0105] The ceramic pumps 23 a and 23 b are each formed of a ceramic thinplate(s). The ceramic pumps 23 a and 23 b include pump-chamber formingportions 24 a and 24 b having a substantially square shape as viewedfrom above; and piezoelectric films 25 a and 25 b fixed to the uppersurfaces of the pump-chamber forming portions 24 a and 24 b,respectively. The pump-chamber forming portions 24 a and 24 b includepump chambers 24 a 1 and 24 b 1 having a shape similar to that of thepump chambers 14 a and 14 b of the drive device 10 according to thefirst embodiment; thin-plate-shaped diaphragms 26 a and 26 b formed onthe pump chambers 24 a 1 and 24 b 1, respectively; and pump-chamberconnection holes 24 a 2 and 24 b 2 which each assume the shape of ahollow cylinder and which connect bottom portions of the pump chambers24 a 1 and 24 b 1 with the upper portions of the channel connectionholes 22 a and 22 b. The pump chambers 24 a 1 and 24 b 1 and thepump-chamber connection holes 24 a 2 and 24 b 2 are filled with theoperation fluid 100 as in the case of the channel connection holes 22 aand 22 b and the channel 13 a.

[0106] The ceramic pumps 23 a and 23 b arepiezoelectric/electrostrictive film type actuators which are fabricatedby utilization of the method and structure disclosed in Japanese PatentApplication Laid-Open Nos. 10-78549 and 7-214779, etc. The ceramic pumps23 a and 23 b are formed on the base body 21 serving as a channelsubstrate and the connection plate 22, in a stacked configuration.

[0107] The operation of the drive device 20 for driving (moving) themovable body 110 is the same as that of the drive device 10. Further,the operation of the drive device 20 for absorbing changes in theinternal pressure due to thermal expansion and contraction of theoperation fluid 100 charged into the pump chambers 24 a 1 and 24 b 1,the pump-chamber connection holes 24 a 2 and 24 b 2, the channelconnection holes 22 a and 22 b, and the channel 13 a is also the same asthat of the drive device 10.

[0108] Next, a method of fabricating the drive device 20 will bedescribed. First, a fabrication process of the ceramic pumps 23 a and 23b, which are piezoelectric/electrostrictive film type actuators, will bedescribed. As shown in FIG. 17, ceramic green sheets 201, 202, and 203are prepared. Subsequently, by means of mechanical machining such aspunching, a window portion 202 a for forming the pump chamber 24 a 1 (24b 1) is formed in the green sheet 202, and a hole portion 203 a isformed in the green sheet 203. The hole portion 203 a is to serve as thepump-chamber connection hole 24 a 2 (24 b 2) for connecting the pumpchamber 24 a 1 (24 b 1) with the channel 13 a via the channel connectionhole 22 a (22 b).

[0109] Subsequently, the green sheets 201, 202, and 203 are stacked andheated under pressure to thereby be fired. Thus, the green sheets 201,202, and 203 are integrated together to thereby form a diaphragmsubstrate 204. Subsequently, a lower electrode 205 and an auxiliaryelectrode 206 as disclosed in Japanese Patent Application Laid-Open(kokai) No. 5-267742 are formed on the substrate 204 The electrode 205and the electrode 206 are formed from a high-melting-point metal and inaccordance with a thick-film forming process, such as screen printing.If necessary, the substrate is subjected to heat treatment such asfiring. A piezoelectric film 207 is formed on the electrodes inaccordance with a thick-film forming process, and finally an upperelectrode 208 is formed. In forming the upper electrode 208, a thin-filmforming process such as sputtering may be used instead of the thick-filmforming process. In the above-described manner, portions correspondingto the ceramic pumps 23 a and 23 b are fabricated.

[0110]FIG. 18 shows a different method for fabricating the portionscorresponding to the above-described ceramic pumps 23 a and 23 b. Inthis method, during the process of fabricating the diaphragm substrate,in place of using the above-described green sheet 202, a spacer layer202 b is formed on the green sheet 203 by means of screen printing insuch a manner that the spacer layer 202 b has a window portion 202 a forforming the pump chamber 24 a 1 (24 b 1) . The remaining portion is thesame as that of the fabrication method having been described withreference to FIG. 17. The details of this fabrication method aredisclosed in Japanese Patent Application Laid-Open No. 9-229013. Thetechnique disclosed in the patent publication enables the depth of thepump chamber 24 a 1 (24 b 1) (the height of the hollow cylinder alongthe Z-axis direction in the assembled state) to be reduced to about 10μm. Therefore, the diaphragm substrate (i.e., the ceramic pumps 23 a and23 b) can have a pump chamber 24 a 1 (24 b 1) of small volume.

[0111] Next, a method of fabricating the base body (channel substrate)21 will be described with reference to FIG. 19. First, an appropriatematerial is selected from plastic, glass, metal, and ceramics, and thensubstrates 211, 212, and 213 are made using the selected material.Subsequently, the channel 13 a, the micro channels 16 a 1 and 16 b 1,and the internal-pressure buffering chamber 15 a are formed in thesubstrates 211, 212, and 213, respectively. Further, an operation fluidinjection hole 213 a is formed in the substrate 213 in such a mannerthat the operation fluid injection hole 213 a penetrates from the bottomwall surface of the internal-pressure buffering chamber 15 a to thelower surface of the substrate 213. A machining method suitable forforming channels, etc. in the substrates 211, 212, and 213 is selectedfrom among punching, etching, laser machining, coining, sandblasting,etc. Subsequently, the substrates 211, 212, and 213 are stacked andbonded by use of epoxy resin or the like to thereby complete the basebody 21.

[0112] Notably, in order to make the thermal expansion coefficient ofthe base body 21 equal, to the extent possible, to that of the ceramicpumps 23 a and 23 b, which are piezoelectric/electrostrictive film typeactuators, the substrates 211, 212, and 213 are preferably formed ofceramic or glass whose expansion coefficient is close to that of theceramic pumps. Further, etching or coining is preferably used fordepression machining; i.e., forming the channel 13 a and theinternal-pressure buffering chamber 15 a having a depth of 200 μm.Alternatively, the substrate 211 having the channel 13 a may be obtainedthrough bonding plates each having a punched window portioncorresponding to the channel 13 a, and a closure plate. Similarly, thesubstrate 213 having the internal-pressure buffering chamber 15 a may beobtained through bonding plates each having a punched window portioncorresponding to the internal-pressure buffering chamber 15 a, and aclosure plate. Meanwhile, the micro channels 16 a 1 and 16 b 1, whichmust have a high aspect ratio, are preferably formed by means of lasermachining or by means of a process of punching a ceramic green sheet inorder to form holes having a high aspect ratio therein, and then firingthe green sheet.

[0113] Meanwhile, as shown in FIG. 20, as in the case of the substrate211, the pair of channel connection holes 22 a and 22 b are formed in aconnection substrate 214, which is to serve as the connection plate 22;and finally, the ceramic pumps 23 a and 23 b(piezoelectric/electrostrictive film type actuators), the connectionsubstrate 214, and the base body 21 are stacked and united by use ofjoining means such as adhesion-bonding, press-bonding, or diffusionjoining.

[0114] During this process, the movable body 110 is placed at apredetermined position within the channel 13 a. When the movable body110 is a vacuole (liquid mass), a material that is insoluble against thevacuole is selected for the operation fluid 100, and the movable body110 is placed at the predetermined position within the channel 13 a byuse of a dispenser or the like. When the movable body is a bubble, aninjection hole for injecting a gas is branched from the channel 13 a,and the bubble and the operation fluid 100 are injected into the channel13 a via the injection hole. There after, the injection hole is sealed.

[0115] Subsequently, the thus-obtained stacked product is placed undervacuum by use of, for example, a vacuum chamber, and a predeterminedamount of the operation fluid 100 is injected from the injection hole213 a into the internal-pressure buffering chamber 15 a by use ofmetering means such as a dispenser. Notably, before injection, theoperation fluid 100 is preferably subjected to vacuum degassing in orderto remove dissolved gases. In order to charge the injected operationfluid 100 into the channel 13 a, the pump chambers 24 a 1 and 24 b 1,etc., via the micro channels 16 a 1 and 16 b 1, the pressure within thechannel is increased to a predetermined level by means of a seal gas120, which is a compressible fluid such as an inert gas, vapor of theoperation fluid 100, or a mixture thereof. Finally, the injection hole213 a is sealed by use of adhesive or the like to thereby obtain thedrive device 20 of the present invention.

[0116] Notably, the depth (height along the Z-axis direction) of theinternal-pressure buffering chamber 15 a is desirably rendered greaterthan the depth of the pump chambers 24 a 1 and 24 b 1, as well asgreater than the depth of the channel 13 a, so as to enable smoothcharging. With this configuration, when the operation fluid 100 isliquid, the radius of curvature of the gas-liquid interface within theinternal-pressure buffering chamber 15 a becomes greater than those ofthe gas-liquid interfaces formed within the pump chambers 24 a 1 and 24b 1 and the channel 13 a under charging, whereby charging can beperformed more smoothly.

[0117] Next, a drive device 30, which serves as a portion of a circuitchangeover switch according to a third embodiment of the presentinvention, will be described. As shown in FIG. 21, which shows avertical cross section of the drive device 30, the drive device 30differs from the drive device 20 of the second embodiment shown in FIG.15 only in that the two pump-chamber forming portions 24 a and 24 b ofthe two ceramic pumps 23 a and 23 b (piezoelectric/electrostrictive filmtype actuators) are replaced with a single pump-chamber forming portion24 c and in that the connection plate 22 provided in the drive device 20is omitted. The drive device 30 can achieve the effect of loweringfabrication cost, by virtue of employing fewer bonded portions andcomponents. In the drive device 20 shown in FIG. 15, the connectionplate 22 can be formed of a transparent glass or a metal plate whichalso serves as an electrode. However, in the drive device 30 shown inFIG. 21, since the connection plate 22 does not exist, the material ofthe pump-chamber forming portion 24 c is restricted to the material ofthe ceramic substrate of the piezoelectric/electrostrictive film typeactuators.

[0118] Next, a drive device 40, which serves as a portion of a circuitchangeover switch according to a fourth embodiment of the presentinvention, will be described. In the drive device 40, whose verticalcross section is shown in FIG. 22, a base body 41 includes a porousmember 16 c in place of the micro channels 16 a 1 and 16 b 1 of thedrive device 20 of the second embodiment shown in FIG. 15; and thechannel 13 a and the internal-pressure buffering chamber 15 a areconnected together via the porous member 16 c. Provision of the porousmember 16 c achieves the same effect as that obtained through formationof a large number of extremely fine (thin) micro channels 16 a 1 and 16b 1. In order to facilitate assembly and improve seal performance, theporous member 16 c preferably has a tapered or stepped side surface, asshown in FIG. 22.

[0119] Next, a drive device 50, which serves as a portion of a circuitchangeover switch according to a fifth embodiment of the presentinvention, will be described. FIG. 23 is a vertical sectional view ofthe drive device 50, and FIG. 24 is a plan view of the drive device 50.Notably, FIG. 23 is a sectional view of the drive device 50 taken alongline 4-4 in FIG. 24. In the drive device 50, in place of thepiezoelectric film 25 b of the ceramic pump 23 b provided in the drivedevice 30 shown in FIG. 21, a ceramic pump 23 c having a pair ofpiezoelectric films 25 c 1 and 25 c 2 is provided. Like thepiezoelectric film 25 a, the piezoelectric films 25 c 1 and 25 c 2 arepolarized in the positive direction of the Z-axis.

[0120] The piezoelectric films 25 c 1 and 25 c 2 each assume anelliptical shape having a long axis along the Y-axis direction as viewedfrom above. The piezoelectric films 25 c 1 and 25 c 2 are fixed onto thediaphragm 26 b, which is a ceramic thin plate, in such a manner thattheir long axes become parallel to each other while being separated by apredetermined distance along the direction of the X-axis. A pump chamber27, which is formed under the diaphragm 26 b, assumes an ellipticalshape having its long axis along the Y-axis direction as viewed fromabove, as in the case of the piezoelectric films 25 c 1 and 25 c 2. Thepiezoelectric films 25 c 1 and 25 c 2 are disposed in such a manner thatthey sandwich the pump chamber 27 as viewed from above, and that aboutone-half of the piezoelectric film 25 c 1 and one-half of thepiezoelectric film 25 c 2 overlap the pump chamber 27 as viewed fromabove. The pump chamber 25 a is also formed such that it assumes anelliptical shape having a long axis along the Y-axis direction as viewedfrom above.

[0121] Next, operation of the drive device 50 configured as describedabove will be described. As shown in FIG. 25, voltages of the samepolarity are applied to the piezoelectric films 25 c 1 and 25 c 2 andthe piezoelectric film 25 a. That is, a drive voltage which changes athigh speed is applied to each of the piezoelectric films 25 a, 25 c 1,and 25 c 2 in such a manner that a positive voltage is applied to theupper electrode and a negative voltage is applied to the lowerelectrode. Thus, the diaphragm 26 a bends and deforms downward due tocontraction of the piezoelectric film 25 a. In contrast, the diaphragm26 b displaces upward at the central portion due to contraction of thepiezoelectric films 25 c 1 and 25 c 2. As a result, the operation fluid100 is pressurized in the pump chamber 24 a 1 and is depressurized inthe pump chamber 27, so that the movable body 110 moves from the pumpchamber 24 a 1 toward the pump chamber 27 (in the positive direction ofthe X-axis)

[0122] Piezoelectric/electrostrictive film type actuators (ceramicpumps) which operate in the above-described manner are disclosed inJapanese Patent Application Laid-Open (kokai) No. 7-202284. Unlike thecase of first through fourth embodiments, in the fifth embodiment (drivedevice 50), voltages of constant polarity are applied to thepiezoelectric films 25 c 1, 25 c 2, and 25 a, and the piezoelectricfilms 25 c 1, 25 c 2, and 25 a can be driven at all times in the samepolarity as that of the polarization electric field thereof. Therefore,the piezoelectric films 25 c 1, 25 c 2, and 25 a can be formed of amaterial of weak coercive field. Further, it should be understood thateven in the case in which the drive device is configured in such amanner that one of the pair of pumps can provide only pressurization orboth pressurization and depressurization and the other pump can providedepressurization only, and the pumps are operated in such a manner, thedrive device may sufficiently provide required functions andperformance. By contrast, when the pump structure of the drive devices10, 20, 30, and 40 of the first through fourth embodiments is employed,film of an electrostrictive material cannot be used as a piezoelectricfilm of a pump which provides depressurization only, unless a specialdrive scheme, such as application of bias voltage, is employed. This isbecause an electrostrictive material does not expand, irrespective ofthe direction of an applied electric field, although it contracts alonga direction perpendicular to the applied electric field, and therefore,the electrostrictive material cannot bend or deform a diaphragm upward.By contrast, in the case of the piezoelectric films 25 c 1 and 25 c 2 ofthe pump 23 c of the drive device 50 according to the fifth embodiment,since the piezoelectric films 25 c 1 and 25 c 2 can bend and deform thediaphragm 26 b upward through their contracting actions to therebyreduce the internal pressure of the pump chamber 27, film of anelectrostrictive material can be used as the piezoelectric films 25 c 1and 25 c 2.

[0123] Notably, as shown in FIG. 26, there may be provided a necessarynumber of pumps 23 d which are similar to the pump 23 c and which havepump chambers of an appropriate shape, depending on the performance ofeach device. In such a case, if a configuration for driving the pumpsindividually is employed, the differential pressure acting on themovable body 110 can be adjusted by, for example, properly changing thenumber of driven pumps, to thereby control the amount of movement and/ormoving speed of the movable body 110.

[0124] Next, an example application of the above-described circuitchangeover switches (drive devices) of the first to fifth embodimentswill be described. A circuit changeover switch 60 shown in FIG. 27includes the above-described drive device 10, and is provided with acommon electrode 61 formed of platinum, gold, nickel, or any othersuitable material, and a pair of changeover electrodes 62 a and 62 bformed of platinum, gold, nickel, or any other suitable material.

[0125] The common electrode 61 is formed on a lower wall surface (wallsurface on the negative side with respect to the Z-axis direction) 13a-1, which is one of the wall surfaces constituting the channel 13 a, insuch a manner that the common electrode 61 is exposed to the channel 13a at a position between the micro channels 16 a 1 and 16 b 1. The commonelectrode 61 is electrically connected to an external electric componentvia an unillustrated connection line (terminal electrode) so that theelectrical potential of the common electrode 61 is transmitted to theelectric component.

[0126] The changeover electrodes 62 a and 62 b have the same shape andare formed on an upper wall surface (wall surface on the positive sidewith respect to the Z-axis direction) 13 a-2, which is another one ofthe wall surfaces constituting the channel 13 a, in such a manner thatthe changeover electrodes 62 a and 62 b are exposed to the channel 13 aso as to face the common electrode 61. The changeover electrodes 62 aand 62 b are mutually separated along the X-axis direction. Thechangeover electrodes 62 a and 62 b are electrically isolated from eachother, and electrically connected to the external electric component viaunillustrated connection lines (terminal electrodes) so that theirelectrical potentials are transmitted to the electric component.Notably, in the following description, the changeover electrode 62 awill be called the first changeover electrode 62 a, and the changeoverelectrode 62 b will be called the second changeover electrode 62 b.

[0127] The movable body 110 is formed of an electrically conductiveliquid metal such as mercury or Ga-base alloy and has a sizesubstantially the same as that of the first changeover electrode 62 a(or the second changeover electrode 62 b) when viewed from the side. Themovable body 110 moves within the channel 13 a while maintaining contactwith the common electrode 61, and selectively comes into contact withthe first changeover electrode 62 a or the second changeover electrode62 b. In other words, the first changeover electrode 62 a and the secondchangeover electrode 62 b are electrically connected to the commonelectrode 61 via the movable body 110.

[0128] Next, operation of the circuit changeover switch 60 will bedescribed. FIG. 27 shows an initial state of the drive device 10 inwhich drive voltage is applied to none of the electrodes of thepiezoelectric films 12 a and 12 b. In this state, the movable body 110comes into contact with the first changeover electrode 62 a and thecommon electrode 61 and does not come into contact with the secondchangeover electrode 62 b. Thus, the first changeover electrode 62 a andthe common electrode 61 are electrically connected to each other.Notably, the position of the movable body 110 in such an initial stateis adjusted by the method having been described with reference to FIGS.9 to 12.

[0129] Meanwhile, during drive, as shown in FIG. 28, a voltage isapplied to the upper and lower electrodes of the piezoelectric film 12 aby means of an unillustrated control circuit in such a manner that theupper electrode assumes a positive polarity and the lower electrodeassumes a negative polarity. Simultaneously, a voltage is applied to theupper and lower electrodes of the piezoelectric film 12 b in such amanner that the upper electrode assumes a negative polarity and thelower electrode assumes a positive polarity. As a result of applicationof the drive voltage, the pump chambers 14 a and 14 b operate; and byvirtue of a pressure difference of the operation fluid 100 generatedupon operation of the pump chambers 14 a and 14 b, the movable body 110moves from the operation chamber 13 a 1 (pump chamber 14 a) toward theoperation chamber 13 a 2 (pump chamber 14 b) (i.e., in the positivedirection of the X-axis) up to a position where the movable body 110comes into contact with the second changeover electrode 62 b, to therebyelectrically connect the second changeover electrode 62 b and the commonelectrode 61.

[0130] Subsequently, the control circuit removes the drive voltageapplied to the respective electrodes of the piezoelectric films 12 a and12 b. As a result, the pump chambers 14 a and 14 b return to theiroriginal states; and, by virtue of a pressure difference of theoperation fluid 100 generated while the pump chambers 14 a and 14 breturn to their original states, the movable body 110 moves from theoperation chamber 13 a 2 toward the operation chamber 13 a 1 (i.e., inthe negative direction of the X-axis) up to a position where the movablebody 110 comes into contact with the first changeover electrode 62 a, tothereby electrically connect the first changeover electrode 62 a and thecommon electrode 61.

[0131] As described above, the circuit changeover switch 61 selectivelyconnects the first changeover electrode 62 a or the second changeoverelectrode 62 b to the common electrode 61 in order to establishelectrical continuity therebetween, by moving the movable body 110. Themovable body 110 exhibits a higher degree of wettability for each of thefirst and second changeover electrodes 62 a and 62 b and a lower degreeof wettability for the wall surface of the channel 13 a at portionswhere the first and second changeover electrodes 62 a and 62 b are notprovided. Therefore, the movable body 110 reliably maintains contactwith the first changeover electrodes 62 a in the initial state andcontact with the second changeover electrodes 62 b in the driven state.

[0132] Next, a specific application of the above-described circuitchangeover switch 60 will be described with reference to FIG. 29. Thesystem shown in FIG. 29 includes two circuit changeover switches eachhaving the same structure as that of the circuit changeover switch 60.These switches are used as a diversity antenna changeover switch and atransmission/reception changeover switch of a portable informationterminal called PDA (Personal Digital Assistant) that is configured toenable radio communications.

[0133] More specifically, the system includes a main antenna 301, adiversity antenna 302, a diversity antenna changeover switch 303 havingthe same structure as that of the circuit changeover switch 60, dtransmission/reception changeover switch 304 having the same structureas that of the circuit changeover switch 60, a power amplifier 305, anRF-IF converter 306, an IF modem 307, and a baseband processor 308.

[0134] The main antenna 301 and the diversity antenna 302 areelectrically connected to a first changeover electrode 303 a and asecond changeover electrode 303 b, respectively, of the diversityantenna changeover switch 303. A common electrode 303 c of the diversityantenna changeover switch 303 is electrically connected to a commonelectrode 304 c of the transmission/reception changeover switch 304. Afirst changeover electrode 304 a of the transmission/receptionchangeover switch 304 is electrically connected to the RF-IF converter(radio frequency—intermediate frequency converter) 306; and a secondchangeover electrode 304 b of the transmission/reception changeoverswitch 304 is electrically connected to the power amplifier 305. Thebaseband processor 308 is electrically connected to the RF-IF converter306 via the IF modem 307 and is electrically connected to the poweramplifier 305. The power amplifier 305 is further connected to the RF-IFconverter 306. The upper and lower electrodes of the respectivepiezoelectric films of the diversity antenna changeover switch 303 andthe transmission/reception changeover switch 304 are connected to anunillustrated control circuit.

[0135] Next, operation of the system will be described. When the systemis in a “reception wait state” in which the system awaits arrival ofradio waves from the outside, the control circuit does not apply anydrive voltage to the upper and lower electrodes of the respectivepiezoelectric films of the diversity antenna changeover switch 303. As aresult, the diversity antenna changeover switch 303 maintains itsinitial state, and a movable body 303 d of the switch 303 stays at theposition shown in FIG. 29 in order to maintain connection between thefirst changeover electrode 303 a and the common electrode 303 c.

[0136] When the system is in the reception wait state, the controlcircuit does not apply any drive voltage to the upper and lowerelectrodes of the respective piezoelectric films of thetransmission/reception changeover switch 304. As a result, thetransmission/reception changeover switch 304 maintains its initialstate, and a movable body 304 d of the switch 304 stays at the positionshown in FIG. 29 in order to maintain connection between the firstchangeover electrode 304 a and the common electrode 304 c.

[0137] As described above, the present system operates in such a mannerthat when the system in the reception wait state, the diversity antennachangeover switch 303 and the transmission/reception changeover switch304 electrically connect the main antenna 301 to the RF-IF converter 306without consuming electrical power.

[0138] In a reception mode, the control circuit selects from the mainantenna 301 and the diversity antenna 302 an antenna suitable forreception (e.g., an antenna which provides high received-radio-waveintensity) . When the main antenna 301 is selected, the control circuitdoes not apply any drive voltage to the upper and lower electrodes ofthe respective piezoelectric films of the diversity antenna changeoverswitch 303. As a result, the diversity antenna changeover switch 303maintains its initial state, and the movable body 303 d of the switch303 stays at the position shown in FIG. 29 in order to maintainconnection between the first changeover electrode 303 a and the commonelectrode 303 c.

[0139] In contrast, when the diversity antenna 302 is selected, thecontrol circuit applies drive voltages to the upper and lower electrodesof the respective piezoelectric films of the diversity antennachangeover switch 303. As a result, the movable body 303 d of thediversity antenna changeover switch 303 moves rightward in FIG. 29 inorder to electrically connect the second changeover electrode 303 b andthe common electrode 303 c. Thus, there is established a state in whichthe diversity antenna 302 can be electrically connected to the RF-IFconverter 306 or the power amplifier 305. Further, in accordance withneeds, the control circuit applies drive voltages to the upper and lowerelectrodes of the respective piezoelectric films of thetransmission/reception changeover switch 304 in order to move themovable body 304 d of the transmission/reception changeover switch 304leftward in FIG. 29, to thereby connect the common electrode 304 c tothe power amplifier 305 via the movable body 304 d and the secondchangeover electrode 304 b. As a result, the received signal isamplified to an appropriate level. Notably, the control circuit may beconfigured in such a manner that no drive voltage is applied to theupper and lower electrodes of the respective piezoelectric films of thetransmission/reception changeover switch 304 throughout the entirereception period, in order to maintain the switch 304 in the initialstate.

[0140] Further, the control circuit may be configured in such a mannerthat in the above-described reception wait state as well, the controlcircuit selects an appropriate antenna as in the reception mode. Even inthe case where the control circuit is configured in the above-describedmanner, the diversity antenna changeover switch 303 can maintain thereception wait state without consuming electrical power, at least whenthe main antenna 301 is determined (selected) to be an appropriateantenna.

[0141] In a transmission mode, the control circuit does not apply anydrive voltage to the upper and lower electrodes of the respectivepiezoelectric films of the diversity antenna changeover switch 303,whereby the diversity antenna changeover switch 303 selects the mainantenna 301 as a transmission antenna. Further, the control circuitapplies drive voltages to the upper and lower electrodes of therespective piezoelectric films of the transmission/reception changeoverswitch 304 in order to connect the common electrode 304 c to the poweramplifier 305 via the movable body 304 d and the second changeoverelectrode 304 b. As a result, a transmission signal amplified by thepower amplifier 305 is transmitted from the main antenna 301. Of course,in the transmission mode as well, drive voltages may be applied to theupper and lower electrodes of the respective piezoelectric films of thediversity antenna changeover switch 303 so as to select the diversityantenna 302 through the diversity antenna changeover switch 303.

[0142] Next, a circuit changeover switch 70 according to the presentinvention which includes a drive device 20′ similar to the drive device20 will be described with reference to FIG. 30. In the circuitchangeover switch 70, a common electrode 71, a first changeoverelectrode 72 a, and a second changeover electrode 72 b, which aresimilar to those of the circuit changeover switch 60, are provided onthe drive device 20′. The circuit changeover switch 70 operates in thesame manner as the circuit changeover switch 60.

[0143] A method of fabricating the circuit changeover switch 70 will bedescribed. The ceramic pumps 23 a and 23 b, which arepiezoelectric/electrostrictive film-type actuators, are fabricated bythe method illustrated in FIG. 17 or FIG. 18. A substrate 21′ isfabricated by the fabrication method illustrated in FIG. 31. Thefabrication method illustrated in FIG. 31 is identical with thefabrication method illustrated in FIG. 19, except that before laminationand bonding of the substrate 211, a substrate 212′ corresponding to thesubstrate 212, and a substrate 213′ corresponding to the substrate 213,a terminal electrode 71 a for leading out (providing) electricalpotential of the common electrode 71, a terminal electrode 72 a 1 forleading out (providing) electrical potential of the first changeoverelectrode 72 a, and a terminal electrode 72 b 1 for leading out(providing) electrical potential of the second changeover electrode 72 bare formed on the upper surface of the substrate 212′ by means of athick-film forming technique such as screen printing.

[0144] Subsequently, the circuit changeover switch 70 is fabricated bythe fabrication method illustrated in FIG. 32. The fabrication methodillustrated in FIG. 32 is identical with the fabrication methodillustrated in FIG. 20, except that the first changeover electrode 72 aand the second changeover electrode 72 b are formed on the lower surfaceof a substrate 214′ corresponding to the substrate 214, by means of athick-film forming technique such as screen printing, and that the firstchangeover electrode 72 a and the second changeover electrode 72 b areelectrically connected to the terminal electrodes 72 a 1 and theterminal electrode 72 b 1, respectively, by use of, for example,electrically conductive adhesive, when the ceramic pumps 23 a and 23 b,the connection substrate 214′, and the substrate 21′ are laminated andunified by coupling means such as bonding, compression bonding, ordiffusion joining. In this manner, the circuit changeover switch 70 isfabricated.

[0145] As described above, a small switch or small relay can befabricated through modification of the drive device of the presentinvention in such a manner that the movable body 110 is formed of aliquid droplet of liquid metal; and a plurality of electrodes 62 a, 62b, etc., which are connected to an external circuit by means of leadwires, are provided on the wall surfaces of the channel 13 a.

[0146] An example of such a switch is a mercury micro relay of a typewhich realizes switching operation through movement of a mercury dropletand which utilizes, as a drive force for moving the mercury droplet,pressure created upon instantaneous generation of a bubble by means ofheating by a micro heater (see, for example, J. Kim et al., Proc. 46thAnnual Int. Relay Conf., Oak Brook, Ill., April 1998, pp. 19-1-19-8).This switch is reported to have various features such as a widefrequency range of DC to 10 GHz, high insulating resistance and lowinsertion loss in the GHz band, and no signal bounce.

[0147] In contrast with such a conventional switch, the above-describedcircuit changeover switch of the present invention utilizespiezoelectric/electrostrictive actuators for generating drive force formoving the movable body 110, which is a droplet of mercury. As a result,as compared with the above-described mercury micro relay of the typewhich utilizes pressure at the time of generation of a bubble, theabove-described circuit changeover switch of the present invention hasadvantages of no heat accumulation and reduced consumption of electricalpower. Therefore, as having been described with reference to FIG. 29,the circuit changeover switch of the present invention can be suitablyused in, for example, PDAs, which have recently been developed toimprove functions and capability of radio communications, in order toserve as an antenna changeover switch for switching antennas used forboth reception and sending (transmission), a circuit changeover switchfor selectively connecting one of a sending (transmission) circuit and areception circuit to an antenna, or any other switch.

[0148] When the circuit changeover switch of the present invention isused in the above-described application, unlike conventionalsemiconductor switches, the circuit changeover switch of the presentinvention provides the following advantages. (a) Since standby or idleelectrical power is not consumed unless reception or transmission isperformed, the overall electrical power consumption of the system can bereduced, and battery life can be extended. (b) Transmission andreception signals hardly deteriorate even in a high frequency band of 1GHz or higher or even 5 GHz or higher. Further, as compared with awet-type mercury lead switch, the circuit changeover switch of thepresent invention has advantages in that no restriction is imposed oninclination angle during use, and a greatly extended life is attained,because the drive sections (movable sections such as pump chambers) areintegrally formed of ceramic.

[0149] Additionally, the circuit changeover switch of the presentinvention is suitable for use as a DC changeover switch. In other words,application of the circuit changeover switch of the present invention isnot limited to switches for high frequency bands.

[0150] Although the common electrode 61 (71) of the above-describedcircuit changeover switch 60 (70) has been described as being a singleelectrode, the common electrode 61 (71) is preferably divided into twopieces corresponding to the first changeover electrode 62 a (72 a) andthe second changeover electrode 62 b (72 b) (i.e., an electrode 61 afacing the first changeover electrode 62 a and an electrode 61 b facingthe second changeover electrode 62 b are provided), as shown in FIG. 33;and the electrodes 61 a and 61 b are electrically connected togetheroutside the circuit changeover switch 60 (70). This configuration ispreferable, because the movable body 110, which is formed of, forexample, mercury having a high degree of wettability for the electrodesurfaces, can move within the channel 13 a with reduced resistance.Further, the first and second changeover electrodes and the commonelectrodes may be exposed to any wall surface (upper surface, lowersurface, side wall surface) of the channel, so long as the insulationamong the electrodes is secured.

[0151] Next, a drive device 500, which serves as a portion of a circuitchangeover switch according to a sixth embodiment of the presentinvention, will be described. FIG. 34 is a plan view of the drive device500; and FIG. 35 is a sectional view of the drive device 500 taken alongline A5-A5 in FIG. 34. The drive device 500 differs from the drivedevice 10 of the first embodiment mainly in that an internal-pressurebuffering chamber is provided at the same vertical position as that ofthe channel and that micro channels extend along the Y-axis (maintainingthe same vertical position) so as to connect the channel and theinternal-pressure buffering chamber.

[0152] Specifically, the drive device 500 comprises a ceramic base body501 of a substantially rectangular parallelepiped shape having sideswhich respectively extend along the X-axis, Y-axis, and Z-axisdirections, which are mutually perpendicular; and a pair ofpiezoelectric films (piezoelectric/electrostrictive elements) 502 a and502 b. As shown in FIG. 35, the base body 501 is formed through aprocess of successively laminating thin plates of ceramic (hereinafterreferred to as “ceramic sheets”) 501-1 to 501-4 and firing the resultantlaminate in such a manner that the base body 501 contains therein achannel forming portion 503, a pair of pump chambers 504 a and 504 b, aninternal-pressure-buffering-chamber-forming portion 505, and a pair ofmicro channel portions 506 a and 506 b.

[0153] The channel forming portion 503 forms a channel 503 a similar tothe channel 13 a of the drive device 10 according to the firstembodiment. The channel 503 a is a hollow space which is defined by sidewall surfaces of a substantially rectangular parallelepiped through holeformed in the ceramic sheet 501-2, the upper surface of the ceramicsheet 501-1, and the lower surface of the ceramic sheet 501-3. The spacehas a substantially rectangular parallelepiped shape having sidesextending along the X-axis, Y-axis, and Z-axis directions, respectively,and has a long axis along the X-axis direction (a rectangular columnarspace whose longitudinal axis lies in a plane parallel to the X-Yplane). As in the case of the channel 13 a, an operation fluid 100 and amovable body 110 are accommodated within the channel 503 a, whereby thechannel 503 a is divided substantially into two operation chambers 503 a1 and 503 a 2 by means of the movable body 110. Within the channel 503a, the movable body 110 is present in the form of a single mass andforms very small clearances S at the four corners of the rectangularcross section of the channel 503 a in order to permit passage of theoperation fluid 100 therethrough (see FIG. 3). Notably, a groove similarto the groove M shown in FIG. 14 may be formed on the wall of thechannel 503 a.

[0154] The pump chambers 504 a and 504 b are similar to the pumpchambers 14 a and 14 b, respectively, of the drive device 10. The pumpchambers 504 a and 504 b are cylindrical spaces defined by side wallsurfaces of through holes formed in the ceramic sheet 501-3, the uppersurface of the ceramic sheet 501-2, and the lower surface of the ceramicsheet 501-4. Thin-plate shaped ceramic diaphragms 507 a and 507 b formedof the ceramic sheet 501-4 are provided above the pump chambers 504 aand 504 b, respectively. In other words, the diaphragms 507 a and 507 bare disposed to constitute respective walls (upper walls) of the pumpchambers 504 a and 504 b (the diaphragms 507 a and 507 b constituteportions of the walls of the pump chambers 504 a and 508 b and to haverespective film surfaces in a common X-Y plane. The ceramic diaphragms507 a and 507 b are identical in configuration with the diaphragms 17 aand 17 b of the above-described drive device 10.

[0155] The piezoelectric film 502 a is formed on the upper surface ofthe diaphragm 507 a, and constitutes a ceramic pump 508 a together withthe pump chamber 504 a and the diaphragm 507 a. The piezoelectric film502 b is formed on the upper surface of the diaphragm 507 b, andconstitutes a ceramic pump 508 b together with the pump chamber 504 band the diaphragm 507 b. The ceramic pumps 508 a and 508 b are identicalin configuration with the ceramic pumps 18 a and 18 b of the drivedevice 10. When a voltage is applied to unillustrated paired electrodesfor the piezoelectric film 502 a (502 b), the piezoelectric film 502 a(502 b) deforms the diaphragm 507 a (507 b) in order to increase ordecrease the volume of the pump chamber 504 a (504 b), to therebypressurize or depressurize the operation fluid 100 within the pumpchamber 504 a (504 b). Notably, the piezoelectric films 502 a and 502 bare each polarized in the positive direction of the Z-axis.

[0156] The internal-pressure-buffering-chamber-forming portion 505 formsan internal-pressure buffering chamber 505 a. As in the case of thechannel 503 a, the internal-pressure buffering chamber 505 a is a hollowspace which is defined by side wall surfaces of a through hole of theceramic sheet 501-2, the upper surface of the ceramic sheet 501-1, andthe lower surface of the ceramic sheet 501-3. The space has asubstantially rectangular parallelepiped shape having sides extendingalong the X-axis, Y-axis, and Z-axis directions, respectively, and has along axis along the X-axis direction (a rectangular columnar space whoselongitudinal axis lies in a plane parallel to the X-Y plane in which thefilm surfaces of the diaphragms 507 a and 507 b are present; i.e., arectangular columnar space having a long axis which is parallel to thelong axis of the channel 503 a and is located at the same verticalposition as the long axis of the channel 503 a). The internal-pressurebuffering chamber 505 a is formed at a position separated from thechannel 503 a in the Y-axis negative direction. The length of theinternal-pressure buffering chamber 505 a as measured along the X-axisdirection is greater than that of the channel 503 a; the length (width)of the internal-pressure buffering chamber 505 a as measured along theY-axis direction is greater than that of the channel 503 a; and thelength (height) of the internal-pressure buffering chamber 505 a asmeasured along the Z-axis direction is equal to that of the channel 503a. A substantially central portion of the chamber 505 a with respect tothe X-axis direction is filled with the above-described operation fluid100; and the peripheral portions thereof are filled with theabove-described compressible fluid for pressure buffering 120.

[0157] The micro channel portion 506 a forms a micro channel 506 a 1. Asin the case of the pump chambers 504 a and 504 b, the micro channel 506a 1 is a substantially rectangular parallelepiped space which is definedby side wall surfaces of a slit-like through hole formed in the ceramicsheet 501-3, the upper surface of the ceramic sheet 501-2, and the lowersurface of the ceramic sheet 501-4 and which has a long axis along theY-axis direction. The micro channel 506 a 1 connects a left-handoperation chamber 503 a 1 (an upper portion of the operation chamber 503a 1) of the channel 503 a with the internal-pressure buffering chamber505 a (an upper portion of the internal-pressure buffering chamber 505a). In other words, the micro channel 506 a 1 extends only along adirection (Y-axis direction) parallel to the X-Y plane in which the filmsurfaces of the diaphragms 507 a and 507 b are present, to therebyconnect the flow chamber 503 a with the internal-pressure bufferingchamber 505 a. The micro channel 506 a 1 is also filled with theoperation fluid 100.

[0158] For example, the micro channel 506 a 1 has specific dimensionssuch that when the micro channel 506 a 1 is sectioned along a plane(i.e., an X-Z plane) perpendicular to the long axis, the height (lengthas measured along the Z-axis direction) of the rectangular cross sectionis 10 μm, and the width (length as measured along the X-axis direction)of the rectangular cross section is 10 μm, and that the length asmeasured along the Y-axis direction (excluding a portion above thechannel 503 a and a portion above the internal-pressure bufferingchamber 505 a) is 500 μm. As in the case of the micro channel 16 a 1,the shape and the dimensions of the micro channel 506 a 1 are selectedin such a manner that a high passage resistance is produced againstabrupt pressure change of the operation fluid 100 within the channel 503a in order to substantially prohibit passage (movement) of the operationfluid 100 toward the internal-pressure buffering chamber 505 a, and onlya small passage resistance is produced against slow pressure change ofthe operation fluid 100 within the channel 503 a, in order tosubstantially permit passage (movement) of the operation fluid 100toward the internal-pressure buffering chamber 505 a (that is, the shapeand the dimensions of the micro channel 506 a 1 are selected so as toprovide a throttle function).

[0159] The micro channel portion 506 b forms a micro channel 506 b 1having the same shape as that of the micro channel 506 a 1 at a positionseparated from the micro channel 506 a 1 by a predetermined distancealong the X-axis direction. The micro channel 506 b 1 extends only alonga direction (Y-axis direction) parallel to the X-Y plane in which thefilm surfaces of the diaphragms 507 a and 507 b are present, to therebyconnect a right-hand operation chamber 503 a 2 (an upper portion of theoperation chamber 503 a 2) of the channel 503 a with theinternal-pressure buffering chamber 505 a (an upper portion of theinternal-pressure buffering chamber 505 a). The micro channel 506 b 1 isalso filled with the operation fluid 100. That is, the micro channel 506b 1 also extends only along the direction (Y-axis direction) parallel tothe X-Y plane in which the film surfaces of the diaphragms 507 a and 507b are present, connects the flow chamber 503 a with theinternal-pressure buffering chamber 505 a, and has the throttle functiondescribed in connection with the micro channel 506 a 1.

[0160] As described above, the operation fluid 100 continuously fillsthe channel 503 a, the pair of pump chambers 504 a and 504 b, the pairof micro channels 506 a 1 and 506 b 1, and a portion of theinternal-pressure buffering chamber 505 a, which communicates with thechannel 503 a via the pair of micro channels 506 a 1 and 506 b 1.Further, the compressible fluid for pressure buffering 120 fills thespaces of the internal-pressure buffering chamber 505 a that are notfilled with the operation fluid 100.

[0161] The operation of the drive device 500 for driving (moving) themovable body 110 is the same as that of the drive device 10. Further,the operation of the drive device 500 for absorbing changes in theinternal pressure of the channel 503 a resulting from thermal expansionand contraction of the operation fluid 100 is also the same as that ofthe drive device 10.

[0162] The thickness (height or length as measured along the Z-axisdirection) of the drive device 500 of the sixth embodiment can be verysmall (reduced), because the drive device 500 is configured to have themicro channels 506 a 1 and 506 b 1 each having a long axis along theY-axis direction, to have the channel 503 a and the internal-pressurebuffering chamber 505 a formed at the same vertical position (in thecommon plane or within the common ceramic sheet 501-2), and to establishcommunication between an upper portion of the channel 503 a and an upperportion of the internal-pressure buffering chamber 505 a by means of themicro channels 506 a 1 and 506 b 1. Further, the drive device 500 can bemade compact, because of a large volume of the space (the total sum ofthe volume of the channel 503 a, those of the pump chambers 504 a and504 b, that of the internal-pressure buffering chamber 505 a, and thoseof the micro channels 506 a 1 and 506 b 1), as compared with the volumeof the base body 501. Further, since the drive device 500 can have asmall thickness and/or an increased surface area relative to the volumethereof, heat generated upon operation can be dissipated to the outsidewith ease. Accordingly, since the entirety of the drive device 500 heatsuniformly (that is, temperature differences among different portions ofthe device are small), the drive device 500 operates stably by virtue ofuniform heating, and has enhanced durability against heat. Next, a drivedevice 510, which serves as a portion of a circuit changeover switchaccording to a seventh embodiment of the present invention, will bedescribed. FIG. 36 is a plan view of the drive device 510; and FIG. 37is a sectional view of the drive device 510 taken along line A6-A6 inFIG. 36. The drive device 510 differs from the drive device 500 mainlyin that a pair of micro channels 516 a 1 and 516 b 1 and a pair ofpump-chamber communication holes 519 a and 519 b are formed in a ceramicsheet 511-3, which is disposed between a ceramic sheet 511-2 in which achannel 513 a is formed and a ceramic sheet 511-4 in which pump chambers514 a and 514 b are formed.

[0163] Specifically, the drive device 510 comprises a ceramic base body511 of a substantially rectangular parallelepiped shape having sideswhich respectively extend along the X-axis, Y-axis, and Z-axisdirections, which are mutually perpendicular; and a pair ofpiezoelectric films (piezoelectric/electrostrictive elements) 512 a and512 b. As shown in FIG. 37, the base body 511 is formed through aprocess of successively laminating ceramic sheets 511-1 to 511-5 andfiring the resultant laminate in such a manner that the base body 511contains therein a channel forming portion 513, aninternal-pressure-buffering-chamber-forming portion 515, the pair ofpump chambers 514 a and 514 b, and the pair of micro channel portions516 a and 516 b.

[0164] The channel forming portion 513 forms a channel 513 a similar tothe channel 503 a of the drive device 500. The channel 513 a is a spacewhich is defined by side wall surfaces of a through hole formed in theceramic sheet 511-2, the upper surface of the ceramic sheet 511-1, andthe lower surface of the ceramic sheet 511-3 and whose longitudinal axiscoincides with the X-axis direction (which has a long axis extendingalong the X-axis direction). As in the case of the channel 503 a, anoperation fluid 100 and a movable body 110 are accommodated within thechannel 513 a, whereby the channel 513 a is divided substantially intotwo operation chambers 513 a 1 and 513 a 2 by means of the movable body110.

[0165] The pump chambers 514 a and 514 b are identical in configurationwith the pump chambers 504 a and 504 b. The pump chambers 514 a and 514b are cylindrical spaces defined by side wall surfaces of through holesformed in the ceramic sheet 511-4, the upper surface of the ceramicsheet 511-3, and the lower surface of the ceramic sheet 511-5. Ceramicdiaphragms 517 a and 517 b formed of the ceramic sheet 511-5 areprovided above the pump chambers 514 a and 514 b, respectively. Thediaphragms 517 a and 517 b are identical in configuration with thediaphragms 507 a and 507 b, and are disposed to constitute portions ofthe walls (upper walls) of the pump chambers 514 a and 514 b and to haverespective film surfaces in a common X-Y plane. Piezoelectric films 512a and 512 b are formed on the upper surfaces of the diaphragms 517 a and517 b, respectively. The piezoelectric films 512 a and 512 b areidentical in configuration with the piezoelectric films 502 a and 502 b.As a result, the pump chamber 514 a, the diaphragm 517 a, and thepiezoelectric film 512 a constitute a ceramic pump 518 a; and the pumpchamber 514 b, the diaphragm 517 b, and the piezoelectric film 512 bconstitute a ceramic pump 518 b. The ceramic pumps 518 a and 518 b areidentical in configuration with the ceramic pumps 508 a and 508 b.

[0166] The internal-pressure-buffering-chamber-forming portion 515 formsan internal-pressure buffering chamber 515 a. The internal-pressurebuffering chamber 515 a is a hollow space which is defined by side wallsurfaces of a through hole of the ceramic sheet 511-2, the upper surfaceof the ceramic sheet 511-1, and the lower surface of the ceramic sheet511-3, which is identical in configuration with the internal-pressurebuffering chamber 505 a, and whose longitudinal axis coincides with theX-axis direction (which has a long axis extending along the X-axisdirection). The internal-pressure buffering chamber 515 a is also formedat a position separated from the channel 513 a in the Y-axis negativedirection. As in the case of the size of the internal-pressure bufferingchamber 505 a relative to the channel 503 a, the internal-pressurebuffering chamber 515 a is greater in size than the channel 513 a. Asubstantially central portion of the chamber 515 a with respect to theX-axis direction is filled with the above-described operation fluid 100;and the peripheral portions thereof are filled with the above-describedcompressible fluid for pressure buffering 120.

[0167] The micro channel portions 516 a and 516 b respectively formmicro channels 516 a 1 and 516 b 1, which are of the same shape andparallel with each other. Each of the micro channels 516 a 1 and 516 b 1is a substantially rectangular parallelepiped space which is defined byside wall surfaces of a slit-like through hole formed in the ceramicsheet 511-3, the upper surface of the ceramic sheet 511-2, and the lowersurface of the ceramic sheet 511-4 and which has a long axis along theY-axis direction. The micro channel 516 a 1 extends from an upperportion of a left-hand operation chamber 513 a 1 of the channel 513 a toan upper portion of the internal-pressure buffering chamber 515 a tothereby connect the left-hand operation chamber 513 a 1 with theinternal-pressure buffering chamber 515 a. The micro channel 516 b 1extends from an upper portion of a right-hand operation chamber 513 a 2of the channel 513 a to an upper portion of the internal-pressurebuffering chamber 515 a to thereby connect the right-hand operationchamber 513 a 2 with the internal-pressure buffering chamber 515 a. Themicro channels 516 a 1 and 516 b 1 are also filled with the operationfluid 100.

[0168] For example, the micro channel 516 a 1 (516 b 1) has specificdimensions such that when the micro channel 516 a 1 is sectioned along aplane (i.e., an X-Z plane) perpendicular to the long axis, the height(length along the Z-axis direction) and width (length along the X-axisdirection) of the rectangular cross section are each 15 μm, and thelength as measured along the Y-axis direction (excluding a portion abovethe channel 513 a and a portion above the internal-pressure bufferingchamber 515 a) is 500 μm. As in the case of the channel 506 a 1, theshape and the dimensions of the micro channel 516 a 1 (516 b 1) areselected so as to provide a throttle function such that a high passageresistance is produced against abrupt pressure change of the operationfluid 100 within the channel 513 a in order to substantially prohibitpassage (movement) of the operation fluid 100 toward theinternal-pressure buffering chamber 515 a, and only a low passageresistance is produced against slow pressure change of the operationfluid 100 within the channel 513 a, in order to substantially permitpassage (movement) of the operation fluid 100 toward theinternal-pressure buffering chamber 515 a.

[0169] The pump chamber communication holes 519 a and 519 b arecylindrical spaces formed of through holes, which are formed in theceramic sheet 511-3, as in the case of the micro channels 516 a 1 and5161 b. The pump chamber communication hole 519 a connects an upperportion of the left-hand operation chamber 513 a 1 of the channel 513 awith the pump chamber 514 a. The pump chamber communication hole 519 bconnects an upper portion of the right-hand operation chamber 513 a 2 ofthe channel 513 a with the pump chamber 514 b. The pump chambercommunication holes 519 a and 519 b are also filled with the operationfluid 100.

[0170] As described above, the operation fluid 100 continuously fillsthe channel 513 a, the pair of pump chambers 514 a and 514 b, the pairof micro channels 516 a 1 and 516 b 1, the pump chamber communicationholes 519 a and 519 b, and a portion of the internal-pressure bufferingchamber 515 a, which communicates with the channel 513 a via the pair ofmicro channels 516 a 1 and 516 b 1. Further, the compressible fluid forpressure buffering 120 fills the spaces of the internal-pressurebuffering chamber 515 a that are not filled with the operation fluid100.

[0171] The operation of the drive device 510 for driving (moving) themovable body 110 is the same as that of the drive device 10. Further,the operation of the drive device 510 for absorbing changes in theinternal pressure of the channel 513 a resulting from thermal expansionand contraction of the operation fluid 100 is also the same as that ofthe drive device 10.

[0172] The thickness (height or length as measured along the Z-axisdirection) of the drive device 510 of the seventh embodiment can be verysmall (reduced), because the drive device 510 is configured to have themicro channels 516 a 1 and 516 b 1 each having a long axis along theY-axis direction, to have the channel 513 a and the internal-pressurebuffering chamber 515 a formed at the same vertical position (in thecommon plane or within the common ceramic sheet 511-2), and to establishcommunication between an upper portion of the channel 513 a and an upperportion of the internal-pressure buffering chamber 515 a by means of themicro channels 516 a 1 and 516 b 1. Further, the drive device 510 can bemade compact, because of a large volume of the space (the total sum ofthe volume of the channel 513 a, those of the pump chambers 514 a and514 b, that of the internal-pressure buffering chamber 515 a, those ofthe micro channels 516 a 1 and 516 b 1, and those of the pump chambercommunication holes 519 a and 519 b), as compared with the volume of thebase body 511. Further, since the drive device 510 can have a smallthickness and/or an increased surface area relative to the volumethereof, heat generated upon operation can be dissipated to the outsidewith ease. Accordingly, the entirety of the drive device 510 heatsuniformly (that is, temperature differences among different portions ofthe device are small), the drive device 510 operates stably by virtue ofuniform heating, and has enhanced durability against heat.

[0173] Next, a drive device 520, which serves as a portion of a circuitchangeover switch according to an eighth embodiment of the presentinvention, will be described. FIG. 38 is a plan view of the drive device520; and FIG. 39 is a sectional view of the drive device 520 taken alongline A7-A7 in FIG. 38. The drive device 520 differs from the drivedevice 500 mainly in that a pair of micro channels are formed in aceramic sheet 521-1, which forms a channel and an internal-pressurebuffering chamber in cooperation with a ceramic sheet 521-2. Therefore,in the following description, structural portions identical with thoseof the drive device 500 are denoted by the same reference numerals,their detailed descriptions are not repeated, and the above-describeddifference will be mainly described.

[0174] The drive device 520 can be obtained through replacement of theceramic sheets 501-2 and 501-3 of the drive device 500 with ceramicsheets 521-1 to 521-3, which are successively laminated on the ceramicsheet 501-1 and fired integrally. The drive device 520 comprises a basebody 521 and a pair of piezoelectric films(piezoelectric/electrostrictive elements) 502 a and 502 b. The base body521 contains therein a channel forming portion 503, aninternal-pressure-buffering-chamber-forming portion 505, a pair of pumpchambers 524 a and 524 b, and a pair of micro channel portions 526 a and526 b.

[0175] The channel forming portion 503 forms a channel 503 a, which isdefined by side wall surfaces of substantially rectangularparallelepiped through holes formed in the ceramic sheets 521-1 and521-2, the upper surface of the ceramic sheet 501-1, and the lowersurface of the ceramic sheet 521-3.

[0176] The pump chambers 524 a and 524 b are identical in configurationwith the pump chambers 504 a and 504 b. The pump chambers 524 a and 524b are cylindrical spaces defined by side wall surfaces of through holesformed in the ceramic sheet 521-3, the upper surface of the ceramicsheet 521-2, and the lower surface of a ceramic sheet 501-4. Ceramicdiaphragms 507 a and 507 b formed of the ceramic sheet 501-4 areprovided above the pump chambers 524 a and 524 b, respectively, in sucha manner that the ceramic diaphragms 507 a and 507 b constitute portionsof the walls (upper walls) of the pump chambers 524 a and 524 b,respectively. Piezoelectric films 502 a and 502 b are formed on theupper surfaces of the diaphragms 507 a and 507 b, respectively. As aresult, the pump chamber 524 a, the diaphragm 507 a, and thepiezoelectric film 502 a constitute a ceramic pump 528 a; and the pumpchamber 524 b, the diaphragm 507 b, and the piezoelectric film 502 bconstitute a ceramic pump 528 b. The ceramic pumps 528 a and 528 b areidentical in configuration with the ceramic pumps 508 a and 508 b.

[0177] The internal-pressure-buffering-chamber-forming portion 505 formsan internal-pressure buffering chamber 505 a, which is defined by sidewall surfaces of substantially rectangular parallelepiped through holesformed in the ceramic sheets 521-1 and 521-2, the upper surface of theceramic sheet 501-1, and the lower surface of the ceramic sheet 521-3,as in the case of the channel 503 a.

[0178] The micro channel portion 526 a forms a micro channel 526 a 1.The micro channel 526 a 1 is a substantially rectangular parallelepipedspace which is defined by side wall surfaces of a slit-like through holeformed in the ceramic sheet 521-1 the upper surface of the ceramic sheet501-1, and the lower surface of the ceramic sheet 521-2 and which has along axis along the Y-axis direction. The micro channel 526 a 1 connectsa left-hand operation chamber 503 a 1 (a side wall portion of theoperation chamber 503 a 1 formed in the ceramic sheet 521-1) of thechannel 503 a with the internal-pressure buffering chamber 505 a (a sidewall portion of the internal-pressure buffering chamber 505 a formed inthe ceramic sheet 521-1). Notably, the micro channel 526 a 1 has thesame dimensions as the micro channel 506 a 1.

[0179] The micro channel portion 526 b forms a micro channel 526 b 1.The micro channel 526 b 1 is identical in shape with the micro channel526 a 1, and is a substantially rectangular parallelepiped space whichis defined by side wall surfaces of a slit-like through hole formed inthe ceramic sheet 521-1, the upper surface of the ceramic sheet 501-1,and the lower surface of the ceramic sheet 521-2, which is located at aposition separated from the micro channel 526 a 1 by a predetermineddistance along the X-axis positive direction, and which has a long axisalong the Y-axis direction. The micro channel 526 b 1 connects aright-hand operation chamber 503 a 2 (a side wall portion of theoperation chamber 503 a 2 formed in the ceramic sheet 521-1) of thechannel 503 a with the internal-pressure buffering chamber 505 a (a sidewall portion of the internal-pressure buffering chamber 505 a formed inthe ceramic sheet 521-1).

[0180] As in the case of the micro channels 506 a 1, 506 b 1, etc., theshape and the dimensions of the micro channels 526 a 1 and 526 b 1 areselected so as to provide a throttle function such that a high passageresistance is produced against abrupt pressure change of the operationfluid 100 within the channel 503 a in order to substantially prohibitpassage (movement) of the operation fluid 100 toward theinternal-pressure buffering chamber 505 a, and only a low passageresistance is produced against slow pressure change of the operationfluid 100 within the channel 503 a in order to substantially permitpassage (movement) of the operation fluid 100 toward theinternal-pressure buffering chamber 505 a.

[0181] In the drive device 520 as well, the operation fluid 100continuously fills the channel 503 a, the pair of pump chambers 524 aand 524 b, the pair of micro channels 526 a 1 and 526 b 1, and a portionof the internal-pressure buffering chamber 505 a, which communicateswith the channel 503 a via the pair of micro channels 526 a 1 and 526 b1. Further, the compressible fluid for pressure buffering 120 fills thespaces of the internal-pressure buffering chamber 505 a that are notfilled with the operation fluid 100.

[0182] The operation of the drive device 520 for driving (moving) themovable body 110 is the same as that of the drive device 10. Further,the operation of the drive device 520 for absorbing changes in theinternal pressure of the channel 503 a resulting from thermal expansionand contraction of the operation fluid 100 is also the same as that ofthe drive device 10. As a result, the drive device 520 have the sameadvantages as does the drive device 500. Further, since the drive device520 is small (thin), as is the drive device 500, the drive device 520provides the same effects as does the drive device 500.

[0183] Next, a drive device 530, which serves as a portion of a circuitchangeover switch according to a ninth embodiment of the presentinvention, will be described. FIG. 40 is a plan view of the drive device530; and FIG. 41 is a sectional view of the drive device 530 taken alongline A8-A8 in FIG. 40. The drive device 530 differs from the drivedevice 520 only in that the ceramic sheets 521-1 and 521-2 of the drivedevice 520 have been replaced with ceramic sheets 531-1 and 531-2successively laminated on a ceramic sheet 501-1 and fired integrally.Therefore, in the following description, structural portions identicalwith those of the drive device 520 are denoted by the same referencenumerals, their detailed descriptions are not repeated, and theabove-described difference will be mainly described.

[0184] In the drive device 530, a channel 503 a and an internal-pressurebuffering chamber 505 a are formed by means of side wall surfaces ofthrough holes formed in the ceramic sheets 531-1 and 531-2, the uppersurface of the ceramic sheet 501-1, and the lower surface of a ceramicsheet 521-3.

[0185] Meanwhile, a micro channel 536 a 1 is a substantially rectangularparallelepiped space which is defined by side wall surfaces of aslit-like through hole formed in the ceramic sheet 531-2, the uppersurface of the ceramic sheet 531-1, and the lower surface of the ceramicsheet 521-3 and which has a long axis along the Y-axis direction. Themicro channel 536 a 1 connects a left-hand operation chamber 503 a 1 (aside wall portion of the operation chamber 503 a 1 formed in the ceramicsheet 531-2) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 531-2). Notably, the microchannel 536 a 1 has the same dimensions as the micro channel 506 a 1.

[0186] A micro channel 536 b 1 is identical in shape with the microchannel 536 a 1. The micro channel 536 b 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a slit-like through hole formed in the ceramic sheet 531-2, the uppersurface of the ceramic sheet 531-1, and the lower surface of the ceramicsheet 521-3, which is located at a position separated from the microchannel 536 a 1 by a predetermined distance along the X-axis positivedirection, and which has a long axis along the Y-axis direction. Themicro channel 536 b 1 connects a right-hand operation chamber 503 a 2 (aside wall portion of the operation chamber 503 a 2 formed in the ceramicsheet 531-2) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 531-2). The functions of themicro channels 536 a 1 and 536 b 1 are the same as those of the microchannels 526 a 1 and 526 b 1.

[0187] The drive device 530 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 520. The drive device 530provides the same operation and advantages as those provided by thedrive device 520, and is a small, reliable device.

[0188] Next, a drive device 540, which serves as a portion of a circuitchangeover switch according to a tenth embodiment of the presentinvention, will be described. FIG. 42 is a plan view of the drive device540; and FIG. 43 is a sectional view of the drive device 540 taken alongline A9-A9 in FIG. 42. The drive device 540 differs from the drivedevice 520 only in that the ceramic sheets 521-1 and 521-2 of the drivedevice 520 have been replaced with ceramic sheets 541-1, 5412, and 541-3successively laminated on a ceramic sheet 501-1 and fired integrally.Therefore, in the following description, structural portions identicalwith those of the drive device 520 are denoted by the same referencenumerals, their detailed descriptions are not repeated, and theabove-described difference will be mainly described.

[0189] In the drive device 540, a channel 503 a and an internal-pressure buffering chamber 505 a are formed by means of side wallsurfaces of through holes formed in the ceramic sheets 541-1, 541-2, and541-3, the upper surface of the ceramic sheet 501-1, and the lowersurface of the ceramic sheet 521-3.

[0190] Meanwhile, the micro channel 546 a 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a slit-like through hole formed in the ceramic sheet 541-2, the uppersurface of the ceramic sheet 541-1, and the lower surface of the ceramicsheet 541-3 and which has a long axis along the Y-axis direction. Themicro channel 546 a 1 connects a left-hand operation chamber 503 a 1 (aside wall portion of the operation chamber 503 a 1 formed in the ceramicsheet 541-2) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 541-2).

[0191] For example, the micro channel 546 a 1 has specific dimensionssuch that when the micro channel 546 a 1 is sectioned along a plane(i.e., an X-Z plane) perpendicular to the long axis, the height (lengthalong the Z-axis direction) of the rectangular cross section is 30 μm,and the width (length along the X-axis direction) of the rectangularcross section is 15 μm, and that the length as measured along the Y-axisdirection (the length of a portion not including the channel 503 a andthe internal-pressure buffering chamber 505 a) is 500 μm.

[0192] A micro channel 546 b 1 is identical in shape with the microchannel 546 a 1. The micro channel 546 b 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a slit-like through hole formed in the ceramic sheet 541-2, the uppersurface of the ceramic sheet 541-1, and the lower surface of the ceramicsheet 541-3, which is located at a position separated from the microchannel 546 a 1 by a predetermined distance along the X-axis positivedirection, and which has a long axis along the Y-axis direction. Themicro channel 546 b 1 connects a right-hand operation chamber 503 a 2 (aside wall portion of the operation chamber 503 a 2 formed in the ceramicsheet 541-2) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 541-2). The functions of themicro channels 546 a 1 and 546 b 1 are the same as those of the microchannels 526 a 1 and 526 b 1.

[0193] The drive device 540 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 520. The drive device 540provides the same operation and advantages as those provided by thedrive device 520, and is a small, reliable device.

[0194] Next, a drive device 550, which serves as a portion of a circuitchangeover switch according to an eleventh embodiment of the presentinvention, will be described. FIG. 44 is a plan view of the drive device550; and FIG. 45 is a sectional view of the drive device 550 taken alongline AA-AA in FIG. 44. The drive device 550 differs from the drivedevice 520 only in that the ceramic sheets 521-1 and 521-2 of the drivedevice 520 have been replaced with a ceramic sheet 551-1 laminated on aceramic sheet 501-1. Therefore, in the following description, structuralportions identical with those of the drive device 520 are denoted by thesame reference numerals, their detailed descriptions are not repeated,and the above-described difference will be mainly described.

[0195] In the drive device 550, a channel 503 a and an internal-pressurebuffering chamber 505 a are formed by means of side wall surfaces ofthrough holes formed in the ceramic sheet 551-1, the upper surface ofthe ceramic sheet 501-1, and the lower surface of a ceramic sheet 521-3.

[0196] Meanwhile, a micro channel 556 a 1 is a substantially rectangularparallelepiped space which is defined by side wall surfaces of aslit-like through hole formed in the ceramic sheet 551-1, the uppersurface of the ceramic sheet 501-1, and the lower surface of the ceramicsheet 521-3 and which has a long axis along the Y-axis direction. Themicro channel 556 a 1 connects a left-hand operation chamber 503 a 1 (aside wall portion of the operation chamber 503 a 1 formed in the ceramicsheet 551-1) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 551-1).

[0197] For example, the micro channel 556 a 1 has specific dimensionssuch that when the micro channel 556 a 1 is sectioned along a plane(i.e., an X-Z plane) perpendicular to the long axis, the height (lengthalong the Z-axis direction) of the rectangular cross section is 50 μm,and the width (length along the X-axis direction) of the rectangularcross section is 15 μm, and that the length as measured along the Y-axisdirection (the length of a portion not including the channel 503 a andthe internal-pressure buffering chamber 505 a) is 500 μm.

[0198] A micro channel 556 b 1 is identical in shape with the microchannel 556 a 1. The micro channel 556 b 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a slit-like through hole formed in the ceramic sheet 551-1, the uppersurface of the ceramic sheet 501-1, and the lower surface of the ceramicsheet 521-3, which is located at a position separated from the microchannel 556 a 1 by a predetermined distance along the X-axis positivedirection, and which has a long axis along the Y-axis direction. Themicro channel 556 b 1 connects a right-hand operation chamber 503 a 2 (aside wall portion of the operation chamber 503 a 2 formed in the ceramicsheet 551-1) of the channel 503 a with the internal-pressure bufferingchamber 505 a (a side wall portion of the internal-pressure bufferingchamber 505 a formed in the ceramic sheet 551-1). The functions of themicro channels 556 a 1 and 556 b 1 are the same as those of the microchannels 526 a 1 and 526 b 1.

[0199] The drive device 550 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 520. The drive device 550provides the same operation and advantages as those provided by thedrive device 520, and is a small, reliable device. Further, by contrastwith the drive devices 520, 530, and 540, the side wall surfaces of thechannel 503 a and the internal-pressure buffering chamber 505 a can beformed by use of the single ceramic sheet 551-1, so that the drivedevice 550 can be fabricated with ease and at low cost.

[0200] Next, a drive device 560, which serves as a portion of a circuitchangeover switch according to a twelfth embodiment of the presentinvention, will be described. FIG. 46 is a plan view of the drive device560; and FIG. 47 is a sectional view of the drive device 560 taken alongline AB-AB in FIG. 46. The drive device 560 differs from the drivedevice 520 only in that the ceramic sheets 521-1 and 521-2 of the drivedevice 520 have been replaced with ceramic sheets 561-1 and 561-2laminated on a ceramic sheet 501-1 and then fired integrally. Therefore,in the following description, structural portions identical with thoseof the drive device 520 are denoted by the same reference numerals,their detailed descriptions are not repeated, and the above-describeddifference will be mainly described.

[0201] In the drive device 560, a channel 503 a and an internal-pressurebuffering chamber 505 a are formed by means of side wall surfaces ofthrough holes formed in the ceramic sheet 561-2, the upper surface ofthe ceramic sheet 561-1, and the lower surface of the ceramic sheet521-3.

[0202] Meanwhile, a micro channel 566 a 1 is a substantially rectangularparallelepiped space which is defined by side wall surfaces of aslit-like through hole formed in the ceramic sheet 561-1, the uppersurface of the ceramic sheet 501-1, and the lower surface of the ceramicsheet 561-2 and which has a long axis along the Y-axis direction. Themicro channel 566 a 1 connects a left-hand operation chamber 503 a 1 (alower portion of the operation chamber 503 a 1) of the channel 503 awith the internal-pressure buffering chamber 505 a (a lower portion ofthe internal-pressure buffering chamber 505 a). The micro channel 566 a1 has the same dimensions as does the micro channel 506 a 1 shown inFIG. 35.

[0203] A micro channel 566 b 1 is identical in shape with the microchannel 566 a 1. The micro channel 566 b 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a slit-like through hole formed in the ceramic sheet 561-1, the uppersurface of the ceramic sheet 501-1, and the lower surface of the ceramicsheet 561-2, which is located at a position separated from the microchannel 566 a 1 by a predetermined distance along the X-axis positivedirection, and which has a long axis along the Y-axis direction. Themicro channel 566 b 1 connects a right-hand operation chamber 503 a 2 (alower portion of the operation chamber 503 a 2) of the channel 503 awith the internal-pressure buffering chamber 505 a (a lower portion ofthe internal-pressure buffering chamber 505 a). The functions of themicro channels 566 a 1 and 566 b 1 are the same as those of the microchannels 526 a 1 and 526 b 1.

[0204] The drive device 560 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 520. The drive device 560provides the same operation and advantages as those provided by thedrive device 520, and is a small, reliable device.

[0205] Next, a drive device 570, which serves as a portion of a circuitchangeover switch according to a thirteenth embodiment of the presentinvention, will be described. FIG. 48 is a plan view of the drive device570; FIG. 49 is a sectional view of the drive device 570 taken alongline AC-AC in FIG. 48; and FIG. 50 is a sectional view of the drivedevice 570 taken along line AD-AD in FIG. 48.

[0206] The drive device 570 differs from the drive device 560 in thatthe ceramic sheets 501-1 and 561-1 of the drive device 560 have beenreplaced with a ceramic sheet 571-1; the ceramic sheet 561-2 of thedrive device 560 have been replaced with a ceramic sheet 571-2; and asingle micro channel is provided. Therefore, in the followingdescription, structural portions identical with those of the drivedevice 560 are denoted by the same reference numerals, their detaileddescriptions are not repeated, and the above-described difference willbe mainly described.

[0207] In the drive device 570, a channel 503 a and an internal-pressurebuffering chamber 505 a are formed by means of side wall surfaces ofthrough holes formed in the ceramic sheet 571-2, the upper surface ofthe ceramic sheet 571-1, and the lower surface of the ceramic sheet521-3. Further, as shown in FIGS. 48 and 50, a groove 570M is formed onthe upper surface of the ceramic sheet 571-1. The groove 570M having along axis extending along the X-axis direction is disposed at asubstantially central portion of a lower wall surface of the channel 503a with respect to the X-axis direction, and provides the same functionas that provided by the groove M shown in FIG. 14.

[0208] Meanwhile, the micro channel 576 a 1 is a substantiallyrectangular parallelepiped space which is defined by side wall surfacesof a rectangular groove formed, through laser machining, on the uppersurface of the ceramic sheet 571-1 and the lower surface of the ceramicsheet 571-2 and which has a long axis along the Y-axis direction. Themicro channel 576 a 1 connects a lower portion of a left-hand operationchamber 503 a 1 of the channel 503 a and the groove 570M with theinternal-pressure buffering chamber 505 a (a lower portion of theinternal-pressure buffering chamber 505 a). The micro channel 576 a 1has the same dimensions as the micro channel 506 a 1 shown in FIG. 35,and provides the same function as that provided by the micro channel 506a 1.

[0209] The drive device 570 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 520. The drive device 570provides the same operation as that provided by the drive device 10-1,which is a modification of the first embodiment and is shown in FIG. 13.As a result, the drive device 570 can serve as a small, reliable deviceas in the case of the drive device 520. Further, since the drive device570 has the single micro channel 576 a 1, labor and time needed formachining of the micro channel can be halved, and the drive device canbe provided inexpensively.

[0210] Next, a drive device 580, which serves as a portion of a circuitchangeover switch according to a fourteenth embodiment of the presentinvention, will be described. FIG. 51 is a plan view of the drive device580; and FIG. 52 is a sectional view of the drive device 580 taken alongline AE-AE in FIG. 51.

[0211] The drive device 580 differs from the drive device 500 of thesixth embodiment shown in FIGS. 34 and 35 in that the ceramic sheet501-3 of the drive device 500 has been replaced with a ceramic sheet581-1 in order to provide bent micro channels. Therefore, in thefollowing description, structural portions identical with those of thedrive device 500 are denoted by the same reference numerals, theirdetailed descriptions are not repeated, and the above-describeddifference will be mainly described.

[0212] In the drive device 580, micro channels 586 a 1 and 586 b 1 aredefined by side wall surfaces of slit-like through holes formed in theceramic sheet 581-1, the upper surface of a ceramic sheet 501-2, and thelower surface of a ceramic sheet 501-4.

[0213] The micro channel 586 a 1 communicates with an upper portion of aleft-hand operation chamber 503 a 1 of the channel 503 a, extends in theY-axis negative direction from the upper portion of the operationchamber 503 a 1, bends at a substantially central portion of the basebody 581 with respect to the Y-axis direction toward the X-axis negativedirection, then extends again in the Y-axis negative direction in orderto communicate with an upper portion of the internal-pressure bufferingchamber 505 a. Similarly, the micro channel 586 b 1 communicates with anupper portion of a right-hand operation chamber 503 a 2 of the channel503 a, extends in the Y-axis negative direction from the upper portionof the operation chamber 503 a 2, bends at a substantially centralportion of the base body 581 with respect to the Y-axis direction towardthe X-axis positive direction, then extends again in the Y-axis negativedirection in order to communicate with an upper portion of theinternal-pressure buffering chamber 505 a.

[0214] The micro channels 586 a 1 and 586 b 1 each have a substantiallyrectangular cross section when taken along a plane (i.e., an X-Z plane)perpendicular to the axial direction. Example dimensions at a portionextending in the Y-axis negative direction are such that the height(length along the Z-axis direction) of the rectangular cross section is10 μm, and the width (length along the X-axis direction) of therectangular cross section is 10 μm. Further, the overall axial length(the overall length of a channel excluding a portion above the channel503 a and a portion above the internal-pressure buffering chamber 505 a)is 700 μm.

[0215] The drive device 580 accommodates a movable body 110, anoperation fluid 100, and a compressible fluid for pressure buffering 120in the same manner as the drive device 500. The drive device 580provides the same operation and advantages as those provided by thedrive device 500, and is a small, reliable device. Further, in the drivedevice 580, the axial length (channel length) of each micro channel isincreased and/or the micro channel is bent in order to attain an effectof increasing passage resistance which is similar to that obtainedthrough reduction of the cross sectional area of the micro channel. As aresult, in the drive device 580, even when a higher passage resistancemust be produced against abrupt pressure change of the operation fluid100, drastic reduction in the cross sectional areas of the microchannels 586 a 1 and 586 b 1 is not required. Therefore, machiningaccuracy involved in formation of micro slits in the ceramic sheet 581-1is not required to increase very much, whereby the drive device can befabricated at low cost.

[0216] Next, a modification of the piezoelectric/electrostrictiveactuators employed in the above-described embodiments will be describedwith reference to an example in which a modifiedpiezoelectric/electrostrictive actuator is used for the drive device 500of the sixth embodiment shown in FIGS. 34 and 35 in order to replace theceramic pump 508 b (508 a). The modified piezoelectric/electrostrictiveactuator includes a plurality of layered piezoelectric films to serve asa pump, and, needless to say, can be used not only as the ceramic pumps508 a and 508 b, but also as actuators (pumps) of other embodiments.

[0217]FIGS. 53 and 54 are enlarged sectional views of apiezoelectric/electrostrictive film actuator 300 of the modificationapplied to the drive device 500 shown in FIGS. 34 and 35, taken alonglines A5-A5 and AF-AF, respectively, in FIG. 34.

[0218] As shown in these drawings, the piezoelectric/electrostrictivefilm actuator 300 includes a first electrode film 301-1, a firstpiezoelectric/electrostrictive film 302-1, a second electrode film301-2, a second piezoelectric/electrostrictive film 3022, a thirdelectrode film 301-3, a third piezoelectric/electrostrictive film 302-3,and a fourth electrode film 301-4, which are successively stacked on theupper surface of the ceramic diaphragm 507 b formed of the ceramic sheet501-4.

[0219] The first electrode film 301-1 and the third electrode film 301-3are connected together to assume the same potential to therebyconstitute a first electrode section. The second electrode film 301-2and the fourth electrode film 301-4 are connected together to assume thesame potential to thereby constitute a second electrode section. Thefirst electrode section and the second electrode section are mutuallyisolated by means of the piezoelectric/electrostrictive films; and as inthe case of the above-described upper and lower electrodes, a drivevoltage is applied to the first and second electrode sections in such amanner that the first and second electrode sections assume differentpolarities.

[0220] The first to fourth electrode films 301-1 to 301-4 are preferablyformed of a metallic material which is solid at room temperature, whichcan endure an oxidizing atmosphere at high temperature of about firingtemperature employed during fabrication of thepiezoelectric/electrostrictive film actuator 300, and which hasexcellent electrical conductivity. Examples of such a metallic materialinclude pure metals such as aluminum, titanium, chromium, iron, cobalt,nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium,rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, andlead; and alloys of these metals. The first to fourth electrode films301-1 to 301-4 may be formed of a cermet material which contains any ofthe above-described materials and into which the same material as thatof the piezoelectric/electrostrictive films or the base body 501 isdispersed. Alternatively, the first to fourth electrode films 301-1 to301-4 may be formed of gold resinated paste, platinum resinated paste,silver resinated paste, or a like material which enables formation ofdense, thin electrode Further, in the above-described multilayer-typepiezoelectric/electrostrictive film actuator, the lowermost electrode(first electrode film 301-1) and intermediate electrodes (second andthird electrode films 301-2 and 301-3) provided between thepiezoelectric/electrostrictive films are preferably formed of anelectrode material that contains platinum, etc., as a main component,and an additive such as zirconia oxide, cerium oxide, or titanium oxide.Although the reasons are unknown, when the lowermost and intermediateelectrodes are formed of these materials, separation between theelectrodes and the piezoelectric/electrostrictive films can beprevented. Notably, the above-mentioned additive is preferably added inan amount of 0.01 to 20% by mass with respect to the entirety of theelectrode material in order to obtain a desired separation preventioneffect.

[0221] Since, in some cases, an increase in thickness of the electrodefilms results in a reduced amount of displacement of thepiezoelectric/electrostrictive film actuator, the electrode films arepreferably thin, in order to maintain a large amount of displacement.Therefore, in general, each of the electrode films preferably has athickness of 15 μm or less, more preferably, 5 μm or less.

[0222] The first to third piezoelectric/electrostrictive films 302-1 to302-3 must be formed of a material which generates electric-fieldinduced distortion such as that due to the piezoelectric effect or thatdue to the electrostrictive effect, but no restriction is imposed interms of whether the material is crystalline or amorphous. Also, asemiconductor, ferroelectric ceramic, or antiferroelectric ceramic maybe used.

[0223] Examples of materials for producingpiezoelectric/electrostrictive film include ceramic materials formedfrom lead zirconate, lead titanate, lead magnesium niobate, lead nickelniobate, lead zinc niobate, lead manganese niobate, lead antimonystannate, lead manganese tungustate, lead cobalt niobate, bariumtitanate, sodium bismuth titanate, potassium sodium niobate, strontiumbismuth tantalate, and mixtures thereof.

[0224] Each of the first to third piezoelectric/electrostrictive films302-1 to 302-3 preferably has a small thickness, in order to obtainlarge displacement at low voltage. For example, eachpiezoelectric/electrostrictive film is designed to have a thickness of100 μm or less, more preferably a thickness of about 3 to 30 μm.Further, when a plurality of piezoelectric/electrostrictive films arelayered on a diaphragm, the thicknesses of thepiezoelectric/electrostrictive films are preferably determined in such amanner that the film thickness decreases gradually toward the uppermostlayer (i.e., with increasing distance from the diaphragm). Morespecifically, the piezoelectric/electrostrictive films are preferablyformed so as to satisfy the following relation:

t _(n) ≦t _(n-1)×0.95

[0225] where t_(n) represents the thickness of the n-thpiezoelectric/electrostrictive film as counted from the lowermostpiezoelectric/electrostrictive film (the piezoelectric/electrostrictivefilm formed immediately on the diaphragm via an electrode film).

[0226] The reason why the thicknesses of thepiezoelectric/electrostrictive films are determined in such a mannerthat the film thickness decreases toward the uppermost layer is asfollows. The amount of distortion of a piezoelectric/electrostrictivefilm increases with the strength of an applied electric field (in otherwords, when a constant drive voltage is applied to thepiezoelectric/electrostrictive film, the amount of distortion increaseswith decreasing thickness of the piezoelectric/electrostrictive film) .Accordingly, when the thicknesses of the piezoelectric/electrostrictivefilms are determined as described above; i.e., in such a manner thatfilm thickness decreases toward the uppermost layer, apiezoelectric/electrostrictive film formed on an upper portion distortsto a greater extent than does a piezoelectric/electrostrictive filmformed on a lower portion. As a result, the efficiency in bending thediaphragm increases, whereby the amount of bending displacement of thediaphragm can be increased.

[0227] The piezoelectric/electrostrictive film actuator 300 can befabricated by a method similar to the fabrication method having beendescribed with reference to FIG. 17 or 18.

[0228] Specifically, the first electrode film 301-1 is first formed onthe upper surface of the ceramic member 501-4 serving as a diaphragm 507b, by means of a method similar to that used to form the above-describedlower electrode 205; and the first piezoelectric/electrostrictive film302-1 is formed on the upper surface of the electrode film 301-1 bymeans of a method similar to that used to form the piezoelectric film207. Subsequently, the second electrode film 301-2 is formed on theupper surface of the first piezoelectric/electrostrictive film 302-1 bymeans of a method similar to that used to form the above-described lowerelectrode 205 or the above-described upper electrode 208; and the secondpiezoelectric/electrostrictive film 302-2 is formed on the upper surfaceof the electrode film 301-2 by means of a method similar to that used toform the piezoelectric film 207. Subsequently, the third electrode film301-3 is formed on the upper surface of the secondpiezoelectric/electrostrictive film 302-2 by means of a method similarto that used to form the above-described lower electrode 205 or theabove-described upper electrode 208; and the thirdpiezoelectric/electrostrictive film 302-3 is formed on the upper surfaceof the electrode film 301-3 by means of a method similar to that used toform the piezoelectric film 207. Finally, the fourth electrode film301-4 is formed by means of a method similar to that used to form theabove-described upper electrode 208.

[0229] As described above, a modification of thepiezoelectric/electrostrictive film actuator, which is applicable to therespective drive devices of the present invention, is thepiezoelectric/electrostrictive film actuator 300, which includes apiezoelectric/electrostrictive element provided on the diaphragm 507 band consisting of piezoelectric/electrostrictive films and electrodefilms, which deforms the diaphragm 507 b by means of displacement(deformation) of the piezoelectric/electrostrictive element, and inwhich the piezoelectric/electrostrictive element is formed in such amanner that the electrode films and the piezoelectric/electrostrictivefilms are laminated alternately, and the uppermost layer and thelowermost layers are formed of electrode films (the first electrodefilm.301-1 and the fourth electrode film 301-4).

[0230] Since the actuator 300 includes a plurality ofpiezoelectric/electrostrictive films, each of which generates force, agreater drive force (a force for deforming the diaphragm) can begenerated upon application of an electrical potential difference betweenthe electrodes (i.e., between the first and second electrode sections),as compared with the case where the same electrical potential differenceis applied between the electrodes (i.e., between the upper and lowerelectrodes) of a piezoelectric/electrostrictive film actuator whichincludes only a single piezoelectric/electrostrictive film between theelectrodes.

[0231] Further, in the piezoelectric/electrostrictive film actuator 300,a plurality of piezoelectric/electrostrictive films are stacked. Thisconfiguration enables easy fabrication of apiezoelectric/electrostrictive element having a high aspect ratio, inwhich the ratio of the dimension in the vertical direction (as measuredalong the Z-axis direction) to the dimensions in the horizontaldirection (as measured along an X-Y plane) is high. Since apiezoelectric/electrostrictive element having a high aspect ratio hashigh rigidity at a portion which causes bending displacement, theelement exhibits an increased response speed. Therefore, throughemployment of the actuator 300, a drive device of enhancedresponsiveness can be obtained.

[0232] Notably, although the piezoelectric/electrostrictive filmactuator 300 includes three piezoelectric/electrostrictive films (andfour electrode films), no limitation is imposed on the number of thepiezoelectric/electrostrictive films, so long as the number is not lessthan two.

[0233] As described above, according to the embodiments of the presentinvention and their modifications, there can be provided drive devicesand circuit changeover switches using the same, which can maintain thefeatures of micro machines such as small size and low power consumption;do not include a mechanical amplification mechanism involving intrinsicproblems of wear and sticking; and can facilitate mass production. Inaddition, since the drive devices (switches) hardly break even when theatmospheric temperature increases, the drive devices (circuit changeoverswitches) have enhanced reliability and durability.

[0234] Notably, the present invention is not limited to theabove-described embodiments, and various modifications may be employedwithin the scope of the present invention. For example, although theabove-described circuit changeover switches each have two changeoverelectrodes, each of the circuit changeover switches may have three ormore changeover electrodes. Further, the changeover electrodes and thecommon electrode may be provided on any wall surface of the channel 13 aso long as these electrodes are exposed to the channel 13 a and areisolated from one another. For example, the changeover electrodes andthe common electrode may be provided on the opposite side wall surfaces.Alternatively, the changeover electrodes may be provided on a side wallsurface, and the common electrode may be provided on the lower wallsurface or the upper wall surface.

[0235] Moreover, while the basic configurations of the respective drivedevices of the present invention are maintained, the films of apiezoelectric/electrostrictive material for deforming diaphragms may bereplaced with films of an antiferroelectric material (antiferroelectricfilm). Further, electrostatic force which is generated betweenelectrodes opposed via a gap and deforming force which is generated in ashape memory alloy heated through application of voltage thereto—whichhave been actively studied in the field of micro machines—may be used inplace of deforming force of piezoelectric film, in order to deform adiaphragm. Even in such a configuration, the combined use of the microchannels 16 a 1, 16 b 1, 16 c and the internal-pressure bufferingchamber 15 a as in the above-described embodiments prevents breakage ofthe drive devices due to variation in atmospheric temperature. Inaddition, the position of the movable body in the initial state can becontrolled through control of the drive voltage (applied voltage).

[0236] Notably, the drive device of the present invention can be used asa device for constructing a so-called rod-less cylinder in the form of amicro machine. As disclosed in, for example, U.S. Pat. No. 3,779,401, arod-less cylinder is configured as follows. A cylinder working sectionis sealed completely; an operation member, which is magnetically coupledwith the working member (the movable body of the present invention)moving within the sealed space, reciprocates outside the sealed space;and movement of the operation member is transmitted to the outside ofthe rod-less cylinder system.

[0237] Accordingly, when the movable body 110 of the present inventionis formed of a magnetic material, and an operation member magneticallycoupled with the movable body 110 is provided outside, there can beobtained a micro rod-less cylinder to which the drive device accordingto the present invention is applied. Further, the drive device of thepresent invention may be configured in such a manner that very smallelectrodes (detection electrodes) are provided within the channel 13 aat numerous locations, and the movable body 110 is formed of anelectrically conductive magnetic material. This configuration enablesdetection of the position of the movable body 110 on the basis of an “ON(close)” or “Off (open)” state of each electrode, to thereby enablecontrol of the stroke position of the micro rod-less cylinder.

[0238] The drive device of the present invention can be applied not onlyto micro machines, such as a micro motor, which are adapted for simplemechanical movement of an object, but also to a wide range of uses ofvarious types of micro machines. For example, a portion or the entiretyof the wall surface of the channel 13 a may be formed of a transparentmaterial, and the movable body 110 may be formed of a bubble, a coloredliquid, a vacuole of a fluorescent liquid, or a very small metal piececapable of reflecting light. In this case, the drive device can be usedas an optical display element. Moreover, when magnetic, optical, orelectrical means for detecting the position of the movable body 110 fromthe outside is provided, the drive device of the present invention canbe used as a memory element. Further, the movable body 110 may be forcedto undergo oscillation motion, and the influence of an external force,such as Coriolis force, exerted on the oscillation motion may be sensedby electrical or optical means. Thus, the drive device can be used as asensor such as a gyroscope.

[0239] The above-described drive device (circuit changeover switch) ofthe present invention can be said to have the following features.Ceramic pumps (23 a, 23 b, 23 c) each including a ceramic diaphragm anda film-type piezoelectric element comprising (consisting of) apiezoelectric/electrostrictive film or an antiferroelectric film andelectrodes are provided on a substrate (11, 21, 41) having a channel (13a). This channel is formed to have a shape for connecting the ceramicpumps, and accommodates a liquid (100) and a movable body (110), such asa bubble, a vacuole, or a micro solid, to be moved. The channel isconnected to a buffering space (15 a) via micro channels (16 a 1, 16 b1, 16 c). When pressurization or depressurization is effected at highspeed by the ceramic pump, the speed at which the liquid enters andreturns from the micro channels is low, so that the micro channelsexhibit an effect for reducing the pressurization or depressurizationwith a time delay. When pressurization or depressurization is effectedat low speed, the liquid freely enters and returns from the microchannels, so that the micro channels exhibit a buffering effect forsuppressing pressure variation within the channel to substantially zero.

1. A circuit changeover switch comprising: a channel forming portion for forming a channel, the channel accommodating an incompressible operation fluid and a movable body made of a substance different from that of the operation fluid, and being substantially divided into two operation chambers by means of the movable body; a pair of pumps each including a pump chamber communicating with the corresponding operation chamber and being filled with the operation fluid, an actuator provided for the pump chamber, and a diaphragm deformed by the actuator, the operation fluid within the pump chamber being pressurized or depressurized through deformation of the diaphragm; an internal-pressure-buffering-chamber-forming portion for forming an internal-pressure buffering chamber which accommodates the operation fluid and a compressible fluid for pressure buffering; and a micro channel portion for forming a micro channel which connects the channel of the channel forming portion and the internal-pressure buffering chamber of the internal-pressure-buffering-chamber-forming portion, the micro channel exhibiting a high passage resistance against abrupt pressure change of the operation fluid within the channel, to thereby substantially prohibit passage of the operation fluid through the micro channel and exhibiting a low passage resistance against slow pressure change of the operation fluid within the channel, to thereby substantially permit passage of the operation fluid through the micro channel.
 2. A circuit changeover switch according to claim 1, wherein the actuator includes a film-type piezoelectric element comprising a piezoelectric/electrostrictive film or an antiferroelectric film and electrodes; and the diaphragm is formed of ceramic.
 3. A circuit changeover switch according to claim 1 or 2, wherein each of the diaphragms of the pumps constitutes a portion of the walls of the corresponding pump chamber and has a film surface in a common plane; the channel of the channel forming portion forms a space whose longitudinal axis lies in a plane parallel to the film surfaces of the diaphragms; the micro channel of the micro channel portion extends along a direction parallel to the film surfaces of the diaphragms; and the internal-pressure buffering chamber of the internal-pressure-buffering-chamber-forming portion forms a space whose longitudinal axis lies in a plane parallel to the film surfaces of the diaphragms and is connected with the channel of the channel forming portion via the micro channel of the micro channel portion. 